Oracle® Fusion Middleware

Performance and Tuning for Oracle WebLogic Server

11g Release 1 (10.3.6)

E13814-08

June 2013

This document is for people who monitor performance and tune the components in a WebLogic Server environment.

Oracle Fusion Middleware Performance and Tuning for Oracle WebLogic Server, 11g Release 1 (10.3.6)

E13814-08

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Contents

Preface

- Documentation Accessibility

- Conventions

1 Introduction and Roadmap

- Document Scope and Audience

- Guide to this Document

- Performance Features of this Release

2 Top Tuning Recommendations for WebLogic Server

- Tune Pool Sizes

- Use the Prepared Statement Cache

- Use Logging Last Resource Optimization

- Tune Connection Backlog Buffering

- Tune the Chunk Size

- Use Optimistic or Read-only Concurrency

- Use Local Interfaces

- Use eager-relationship-caching

- Tune HTTP Sessions

- Tune Messaging Applications

3 Performance Tuning Roadmap

- Performance Tuning Roadmap

- Understand Your Performance Objectives

- Measure Your Performance Metrics

- Monitor Disk and CPU Utilization

- Monitor Data Transfers Across the Network

- Locate Bottlenecks in Your System

- Minimize Impact of Bottlenecks

- Tune Your Application

- Tune your DB

- Tune WebLogic Server Performance Parameters

- Tune Your JVM

- Tune the Operating System

- Achieve Performance Objectives

- Tuning Tips

4 Operating System Tuning

5 Tuning Java Virtual Machines (JVMs)

- JVM Tuning Considerations

- Which JVM for Your System?

- Changing To a Different JVM

- Garbage Collection

- VM Heap Size and Garbage Collection

- Choosing a Garbage Collection Scheme

- Using Verbose Garbage Collection to Determine Heap Size

- Specifying Heap Size Values

- Tuning Tips for Heap Sizes

- JRockit JVM Heap Size Options

- Other JRockit VM Options

- Java HotSpot VM Heap Size Options

- Other Java HotSpot VM Options

- Automatically Logging Low Memory Conditions

- Manually Requesting Garbage Collection

- Requesting Thread Stacks

- Enable Spinning for IA32 Platforms

- Sun JDK

- JRockit

6 Tuning WebLogic Diagnostic Framework and JRockit Flight Recorder Integration

- Using JRockit Flight Recorder

- Using WLDF

- Using JRockit controls outside of WLDF to control the default JVM recording

- Tuning Considerations

7 Tuning WebLogic Server

- Setting Java Parameters for Starting WebLogic Server

- Development vs. Production Mode Default Tuning Values

- Deployment

- On-demand Deployment of Internal Applications

- Use FastSwap Deployment to Minimize Redeployment Time

- Generic Overrides

- Thread Management

- Tuning a Work Manager

- How Many Work Managers are Needed?

- What are the SLA Requirements for Each Work Manager?

- Tuning Execute Queues

- Understanding the Differences Between Work Managers and Execute Queues

- Migrating from Previous Releases

- Tuning the Stuck Thread Detection Behavior

- Tuning Network I/O

- Tuning Muxers

- Java Muxer

- Native Muxers

- Non-Blocking IO Muxer

- Which Platforms Have Performance Packs?

- Enabling Performance Packs

- Changing the Number of Available Socket Readers

- Network Channels

- Reducing the Potential for Denial of Service Attacks

- Tuning Message Size

- Tuning Complete Message Timeout

- Tuning Number of File Descriptors

- Tune the Chunk Parameters

- Tuning Connection Backlog Buffering

- Tuning Cached Connections

- Setting Your Compiler Options

- Compiling EJB Classes

- Setting JSP Compiler Options

- Precompile JSPs

- Optimize Java Expressions

- Using WebLogic Server Clusters to Improve Performance

- Scalability and High Availability

- How to Ensure Scalability for WebLogic Clusters

- Database Bottlenecks

- Session Replication

- Asynchronous HTTP Session Replication

- Asynchronous HTTP Session Replication using a Secondary Server

- Asynchronous HTTP Session Replication using a Database

- Invalidation of Entity EJBs

- Invalidation of HTTP sessions

- JNDI Binding, Unbinding and Rebinding

- Running Multiple Server Instances on Multi-Core Machines

- Monitoring a WebLogic Server Domain

- Using the Administration Console to Monitor WebLogic Server

- Using the WebLogic Diagnostic Framework

- Using JMX to Monitor WebLogic Server

- Using WLST to Monitor WebLogic Server

- Resources to Monitor WebLogic Server

- Third-Party Tools to Monitor WebLogic Server

- Tuning Class and Resource Loading

- Filtering Loader Mechanism

- Class Caching

- Server Migration with Database Leasing on RAC Clusters

8 Tuning the WebLogic Persistent Store

- Overview of Persistent Stores

- Using the Default Persistent Store

- Using Custom File Stores and JDBC Stores

- Using a JDBC TLOG Store

- Using JMS Paging Stores

- Using Flash Storage to Page JMS Messages

- Using Diagnostic Stores

- Best Practices When Using Persistent Stores

- Tuning JDBC Stores

- Tuning File Stores

- Basic Tuning Information

- Tuning a File Store Direct-Write-With-Cache Policy

- Using Flash Storeage to Increase Performance

- Additional Considerations

- Tuning the File Store Direct-Write Policy

- Tuning the File Store Block Size

- Setting the Block Size for a File Store

- Determining the File Store Block Size

- Determining the File System Block Size

- Converting a Store with Pre-existing Files

- Using a Network File System

- Configuring Synchronous Write Policies

- Test Server Restart Behavior

- Handling NFS Locking Errors

- Solution 1 - Copying Data Files to Remove NFS Locks

- Solution 2 - Disabling File Locks in WebLogic Server File Stores

9 DataBase Tuning

- General Suggestions

- Database-Specific Tuning

- Oracle

- Microsoft SQL Server

- Sybase

10 Tuning WebLogic Server EJBs

- General EJB Tuning Tips

- Tuning EJB Caches

- Tuning the Stateful Session Bean Cache

- Tuning the Entity Bean Cache

- Transaction-Level Caching

- Caching between Transactions

- Ready Bean Caching

- Tuning the Query Cache

- Tuning EJB Pools

- Tuning the Stateless Session Bean Pool

- Tuning the MDB Pool

- Tuning the Entity Bean Pool

- CMP Entity Bean Tuning

- Use Eager Relationship Caching

- Using Inner Joins

- Use JDBC Batch Operations

- Tuned Updates

- Using Field Groups

- include-updates

- call-by-reference

- Bean-level Pessimistic Locking

- Concurrency Strategy

- Tuning In Response to Monitoring Statistics

- Cache Miss Ratio

- Lock Waiter Ratio

- Lock Timeout Ratio

- Pool Miss Ratio

- Destroyed Bean Ratio

- Pool Timeout Ratio

- Transaction Rollback Ratio

- Transaction Timeout Ratio

- Using the JDT Compiler

11 Tuning Message-Driven Beans

- Use Transaction Batching

- MDB Thread Management

- Determining the Number of Concurrent MDBs

- Selecting a Concurrency Strategy

- Thread Utilization When Using WebLogic Destinations

- Limitations for Multi-threaded Topic MDBs

- Best Practices for Configuring and Deploying MDBs Using Distributed Topics

- Using MDBs with Foreign Destinations

- Concurrency for MDBs that Process Messages from Foreign Destinations

- Thread Utilization for MDBs that Process Messages from Foreign Destinations

- Token-based Message Polling for Transactional MDBs Listening on Queues/Topics

- Compatibility for WLS 10.0 and Earlier-style Polling

12 Tuning Data Sources

- Tune the Number of Database Connections

- Waste Not

- Use Test Connections on Reserve with Care

- Cache Prepared and Callable Statements

- Using Pinned-To-Thread Property to Increase Performance

- Database Listener Timeout under Heavy Server Loads

- Disable Wrapping of Data Type Objects

- Advanced Configurations for Oracle Drivers and Databases

- Use Best Design Practices

13 Tuning Transactions

- Logging Last Resource Transaction Optimization

- LLR Tuning Guidelines

- Read-only, One-Phase Commit Optimizations

14 Tuning WebLogic JMS

- JMS Performance & Tuning Check List

- Handling Large Message Backlogs

- Improving Message Processing Performance

- Controlling Message Production

- Drawbacks to Controlling Message Production

- Cache and Re-use Client Resources

- Tuning Distributed Queues

- Tuning Topics

- Tuning for Large Messages

- Defining Quota

- Quota Resources

- Destination-Level Quota

- JMS Server-Level Quota

- Blocking Senders During Quota Conditions

- Defining a Send Timeout on Connection Factories

- Specifying a Blocking Send Policy on JMS Servers

- Tuning MessageMaximum

- Tuning MessageMaximum Limitations

- Setting Maximum Message Size for Network Protocols

- Compressing Messages

- Paging Out Messages To Free Up Memory

- Specifying a Message Paging Directory

- Tuning the Message Buffer Size Option

- Controlling the Flow of Messages on JMS Servers and Destinations

- How Flow Control Works

- Configuring Flow Control

- Flow Control Thresholds

- Handling Expired Messages

- Defining a Message Expiration Policy

- Configuring an Expiration Policy on Topics

- Configuring an Expiration Policy on Queues

- Configuring an Expiration Policy on Templates

- Defining an Expiration Logging Policy

- Expiration Log Output Format

- Tuning Active Message Expiration

- Configuring a JMS Server to Actively Scan Destinations for Expired Messages

- Tuning Applications Using Unit-of-Order

- Best Practices

- Using UOO and Distributed Destinations

- Migrating Old Applications to Use UOO

- Using One-Way Message Sends

- Configure One-Way Sends On a Connection Factory

- One-Way Send Support In a Cluster With a Single Destination

- One-Way Send Support In a Cluster With Multiple Destinations

- When One-Way Sends Are Not Supported

- Different Client and Destination Hosts

- XA Enabled On Client's Host Connection Factory

- Higher QOS Detected

- Destination Quota Exceeded

- Change In Server Security Policy

- Change In JMS Server or Destination Status

- Looking Up Logical Distributed Destination Name

- Hardware Failure

- One-Way Send QOS Guidelines

- Tuning the Messaging Performance Preference Option

- Messaging Performance Configuration Parameters

- Compatibility With the Asynchronous Message Pipeline

- Client-side Thread Pools

- Best Practices for JMS .NET Client Applications

15 Tuning WebLogic JMS Store-and-Forward

- Best Practices

- Tuning Tips

16 Tuning WebLogic Message Bridge

- Best Practices

- Changing the Batch Size

- Changing the Batch Interval

- Changing the Quality of Service

- Using Multiple Bridge Instances

- Changing the Thread Pool Size

- Avoiding Durable Subscriptions

- Co-locating Bridges with Their Source or Target Destination

- Changing the Asynchronous Mode Enabled Attribute

17 Tuning Resource Adapters

- Classloading Optimizations for Resource Adapters

- Connection Optimizations

- Thread Management

- InteractionSpec Interface

18 Tuning Web Applications

- Best Practices

- Disable Page Checks

- Use Custom JSP Tags

- Precompile JSPs

- Disable Access Logging

- Use HTML Template Compression

- Use Service Level Agreements

- Related Reading

- Session Management

- Managing Session Persistence

- Minimizing Sessions

- Aggregating Session Data

- Pub-Sub Tuning Guidelines

19 Tuning Web Services

- Web Services Best Practices

- Tuning Web Service Reliable Messaging Agents

- Tuning Heavily Loaded Systems to Improve Web Service Performance

- Setting the Work Manager Thread Pool Minimum Size Constraint

- Setting the Buffering Sessions

- Releasing Asynchronous Resources

20 Tuning WebLogic Tuxedo Connector

- Configuration Guidelines

- Best Practices

A Using the WebLogic 8.1 Thread Pool Model

- How to Enable the WebLogic 8.1 Thread Pool Model

- Tuning the Default Execute Queue

- Should You Modify the Default Thread Count?

- Using Execute Queues to Control Thread Usage

- Creating Execute Queues

- Modifying the Thread Count

- Tuning Execute Queues for Overflow Conditions

- Assigning Servlets and JSPs to Execute Queues

- Assigning EJBs and RMI Objects to Execute Queues

- Monitoring Execute Threads

- Allocating Execute Threads to Act as Socket Readers

- Setting the Number of Socket Reader Threads For a Server Instance

- Setting the Number of Socket Reader Threads on Client Machines

- Tuning the Stuck Thread Detection Behavior

B Capacity Planning

- Capacity Planning Factors

- Programmatic and Web-based Clients

- RMI and Server Traffic

- SSL Connections and Performance

- WebLogic Server Process Load

- Database Server Capacity and User Storage Requirements

- Concurrent Sessions

- Network Load

- Clustered Configurations

- Server Migration

- Application Design

- Assessing Your Application Performance Objectives

- Hardware Tuning

- Benchmarks for Evaluating Performance

- Supported Platforms

- Network Performance

- Determining Network Bandwidth

- Related Information

Preface

This preface describes the document accessibility features and conventions used in this guide—Performance and Tuning for Oracle WebLogic Server.

Documentation Accessibility

For information about Oracle's commitment to accessibility, visit the Oracle Accessibility Program website at http://www.oracle.com/pls/topic/lookup?ctx=acc&id=docacc.

Access to Oracle Support

Oracle customers have access to electronic support through My Oracle Support. For information, visit http://www.oracle.com/pls/topic/lookup?ctx=acc&id=info or visit http://www.oracle.com/pls/topic/lookup?ctx=acc&id=trs if you are hearing impaired.

Conventions

The following text conventions are used in this document:

Convention

Meaning

boldface

Boldface type indicates graphical user interface elements associated with an action, or terms defined in text or the glossary.

italic

Italic type indicates book titles, emphasis, or placeholder variables for which you supply particular values.

monospace

Monospace type indicates commands within a paragraph, URLs, code in examples, text that appears on the screen, or text that you enter.

1 Introduction and Roadmap

This chapter describes the contents and organization of this guide—Performance and Tuning for Oracle WebLogic Server.

- Document Scope and Audience

- Guide to this Document

- Performance Features of this Release

Document Scope and Audience

This document is written for people who monitor performance and tune the components in a WebLogic Server environment. It is assumed that readers know server administration and hardware performance tuning fundamentals, WebLogic Server, XML, and the Java programming language.

Guide to this Document

- This chapter, Chapter 1, "Introduction and Roadmap," introduces the organization of this guide.

- Chapter 2, "Top Tuning Recommendations for WebLogic Server," discusses the most frequently recommended steps for achieving optimal performance tuning for applications running on WebLogic Server.

- Chapter 3, "Performance Tuning Roadmap," provides a roadmap to help tune your application environment to optimize performance.

- Chapter 4, "Operating System Tuning," discusses operating system issues.

- Chapter 5, "Tuning Java Virtual Machines (JVMs)," discusses JVM tuning considerations.

- Chapter 6, "Tuning WebLogic Diagnostic Framework and JRockit Flight Recorder Integration," provides information on how WebLogic Diagnostic Framework (WLDF) works with JRockit Mission Control Flight Recorder.

- Chapter 7, "Tuning WebLogic Server," contains information on how to tune WebLogic Server to match your application needs.

- Chapter 8, "Tuning the WebLogic Persistent Store," provides information on how to tune a persistent store.

- Chapter 9, "DataBase Tuning," provides information on how to tune your data base.

- Chapter 10, "Tuning WebLogic Server EJBs," provides information on how to tune applications that use EJBs.

- Chapter 11, "Tuning Message-Driven Beans," provides information on how to tune Message-Driven beans.

- Chapter 12, "Tuning Data Sources," provides information on how to tune JDBC applications.

- Chapter 13, "Tuning Transactions," provides information on how to tune Logging Last Resource transaction optimization.

- Chapter 14, "Tuning WebLogic JMS," provides information on how to tune applications that use WebLogic JMS.

- Chapter 15, "Tuning WebLogic JMS Store-and-Forward," provides information on how to tune applications that use JMS Store-and-Forward.

- Chapter 16, "Tuning WebLogic Message Bridge," provides information on how to tune applications that use the Weblogic Message Bridge.

- Chapter 17, "Tuning Resource Adapters," provides information on how to tune applications that use resource adaptors.

- Chapter 18, "Tuning Web Applications," provides best practices for tuning WebLogic Web applications and application resources:

- Chapter 19, "Tuning Web Services," provides information on how to tune applications that use Web services.

- Chapter 20, "Tuning WebLogic Tuxedo Connector," provides information on how to tune applications that use WebLogic Tuxedo Connector.

- Appendix A, "Using the WebLogic 8.1 Thread Pool Model," provides information on using execute queues.

- Appendix B, "Capacity Planning," provides an introduction to capacity planning.

Performance Features of this Release

WebLogic Server introduces the following performance enhancements:

- Tuning a File Store Direct-Write-With-Cache Policy

- Using a Network File System

- Tuning WebLogic Diagnostic Framework and JRockit Flight Recorder Integration

2 Top Tuning Recommendations for WebLogic Server

This chapter provides a short list of top performance tuning recommendations. Tuning WebLogic Server and your WebLogic Server application is a complex and iterative process. To get you started, we have created a short list of recommendations to help you optimize your application's performance. These tuning techniques are applicable to nearly all WebLogic applications.

- Tune Pool Sizes

- Use the Prepared Statement Cache

- Use Logging Last Resource Optimization

- Tune Connection Backlog Buffering

- Tune the Chunk Size

- Use Optimistic or Read-only Concurrency

- Use Local Interfaces

- Use eager-relationship-caching

- Tune HTTP Sessions

- Tune Messaging Applications

Tune Pool Sizes

Provide pool sizes (such as pools for JDBC connections, Stateless Session EJBs, and MDBs) that maximize concurrency for the expected thread utilization.

- For WebLogic Server releases 9.0 and higher—A server instance uses a self-tuned thread-pool. The best way to determine the appropriate pool size is to monitor the pool's current size, shrink counts, grow counts, and wait counts. See Thread Management. Tuning MDBs are a special case, please see Chapter 11, "Tuning Message-Driven Beans".

- For releases prior to WebLogic Server 9.0—In general, the number of connections should equal the number of threads that are expected to be required to process the requests handled by the pool. The most effective way to ensure the right pool size is to monitor it and make sure it does not shrink and grow. See How to Enable the WebLogic 8.1 Thread Pool Model.

Use the Prepared Statement Cache

The prepared statement cache keeps compiled SQL statements in memory, thus avoiding a round-trip to the database when the same statement is used later. See Chapter 12, "Tuning Data Sources".

Use Logging Last Resource Optimization

When using transactional database applications, consider using the JDBC data source Logging Last Resource (LLR) transaction policy instead of XA. The LLR optimization can significantly improve transaction performance by safely eliminating some of the 2PC XA overhead for database processing, especially for two-phase commit database insert, update, and delete operations. For more information, see Chapter 12, "Tuning Data Sources".

Tune Connection Backlog Buffering

You can tune the number of connection requests that a WebLogic Server instance accepts before refusing additional requests. This tunable applies primarily for Web applications. See Tuning Connection Backlog Buffering.

Tune the Chunk Size

A chunk is a unit of memory that the WebLogic Server network layer, both on the client and server side, uses to read data from and write data to sockets. A server instance maintains a pool of these chunks. For applications that handle large amounts of data per request, increasing the value on both the client and server sides can boost performance. See Tune the Chunk Parameters.

Use Optimistic or Read-only Concurrency

Use optimistic concurrency with cache-between-transactions or read-only concurrency with query-caching for CMP EJBs wherever possible. Both of these two options leverage the Entity Bean cache provided by the EJB container.

- Optimistic-concurrency with cache-between-transactions work best with read-mostly beans. Using verify-reads in combination with these provides high data consistency guarantees with the performance gain of caching. See Chapter 10, "Tuning WebLogic Server EJBs".

- Query-caching is a WebLogic Server 9.0 feature that allows the EJB container to cache results for arbitrary non-primary-key finders defined on read-only EJBs. All of these parameters can be set in the application/module deployment descriptors. See Concurrency Strategy.

Use Local Interfaces

Use local-interfaces or use call-by-reference semantics to avoid the overhead of serialization when one EJB calls another or an EJB is called by a servlet/JSP in the same application. Note the following:

- In release prior to WebLogic Server 8.1, call-by-reference is turned on by default. For releases of WebLogic Server 8.1 and higher, call-by-reference is turned off by default. Older applications migrating to WebLogic Server 8.1 and higher that do not explicitly turn on call-by-reference may experience a drop in performance.

- This optimization does not apply to calls across different applications.

Use eager-relationship-caching

Use eager-relationship-caching wherever possible. This feature allows the EJB container to load related beans using a single SQL statement. It improves performance by reducing the number of database calls to load related beans in transactions when a bean and it's related beans are expected to be used in that transaction. See Chapter 10, "Tuning WebLogic Server EJBs".

Tune HTTP Sessions

Optimize your application so that it does as little work as possible when handling session persistence and sessions. You should also design a session management strategy that suits your environment and application. See Session Management.

Tune Messaging Applications

Oracle provides messaging users a rich set of performance tunables. In general, you should always configure quotas and paging. See:

- Chapter 8, "Tuning the WebLogic Persistent Store"

- Chapter 14, "Tuning WebLogic JMS"

- Chapter 15, "Tuning WebLogic JMS Store-and-Forward"

- Chapter 16, "Tuning WebLogic Message Bridge"

3 Performance Tuning Roadmap

This chapter provides a tuning roadmap and tuning tips for you can use to improve system performance:

- Performance Tuning Roadmap

- Tuning Tips

Performance Tuning Roadmap

The following steps provide a roadmap to help tune your application environment to optimize performance:

1. Understand Your Performance Objectives

2. Measure Your Performance Metrics

3. Locate Bottlenecks in Your System

4. Minimize Impact of Bottlenecks

5. Achieve Performance Objectives

Understand Your Performance Objectives

To determine your performance objectives, you need to understand the application deployed and the environmental constraints placed on the system. Gather information about the levels of activity that components of the application are expected to meet, such as:

- The anticipated number of users.

- The number and size of requests.

- The amount of data and its consistency.

- Determining your target CPU utilization.
Your target CPU usage should not be 100%, you should determine a target CPU utilization based on your application needs, including CPU cycles for peak usage. If your CPU utilization is optimized at 100% during normal load hours, you have no capacity to handle a peak load. In applications that are latency sensitive and maintaining the ability for a fast response time is important, high CPU usage (approaching 100% utilization) can reduce response times while throughput stays constant or even increases because of work queuing up in the server. For such applications, a 70% - 80% CPU utilization recommended. A good target for non-latency sensitive applications is about 90%.

Performance objectives are limited by constraints, such as

- The configuration of hardware and software such as CPU type, disk size vs. disk speed, sufficient memory.
There is no single formula for determining your hardware requirements. The process of determining what type of hardware and software configuration is required to meet application needs adequately is called capacity planning. Capacity planning requires assessment of your system performance goals and an understanding of your application. Capacity planning for server hardware should focus on maximum performance requirements. See Appendix B, "Capacity Planning."

- The ability to interoperate between domains, use legacy systems, support legacy data.

- Development, implementation, and maintenance costs.

You will use this information to set realistic performance objectives for your application environment, such as response times, throughput, and load on specific hardware.

Measure Your Performance Metrics

After you have determined your performance criteria in Understand Your Performance Objectives, take measurements of the metrics you will use to quantify your performance objectives. The following sections provide information on measuring basic performance metrics:

- Monitor Disk and CPU Utilization

- Monitor Data Transfers Across the Network

Monitor Disk and CPU Utilization

Run your application under a high load while monitoring the:

- Application server (disk and CPU utilization)

- Database server (disk and CPU utilization)

The goal is to get to a point where the application server achieves your target CPU utilization. If you find that the application server CPU is under utilized, confirm whether the database is bottle necked. If the database CPU is 100 percent utilized, then check your application SQL calls query plans. For example, are your SQL calls using indexes or doing linear searches? Also, confirm whether there are too many ORDER BY clauses used in your application that are affecting the database CPU. See Chapter 4, "Operating System Tuning".

If you discover that the database disk is the bottleneck (for example, if the disk is 100 percent utilized), try moving to faster disks or to a RAID (redundant array of independent disks) configuration, assuming the application is not doing more writes then required.

Once you know the database server is not the bottleneck, determine whether the application server disk is the bottleneck. Some of the disk bottlenecks for application server disks are:

- Persistent Store writes

- Transaction logging (tlogs)

- HTTP logging

- Server logging

The disk I/O on an application server can be optimized using faster disks or RAID, disabling synchronous JMS writes, using JTA direct writes for tlogs, or increasing the HTTP log buffer.

Monitor Data Transfers Across the Network

Check the amount of data transferred between the application and the application server, and between the application server and the database server. This amount should not exceed your network bandwidth; otherwise, your network becomes the bottleneck. See Operating System Tuning.

Locate Bottlenecks in Your System

If you determine that neither the network nor the database server is the bottleneck, start looking at your operating system, JVM, and WebLogic Server configurations. Most importantly, is the machine running WebLogic Server able to get your target CPU utilization with a high client load? If the answer is no, then check if there is any locking taking place in the application. You should profile your application using a commercially available tool (for example, JProbe or OptimizeIt) to pinpoint bottlenecks and improve application performance.

Tip:

Even if you find that the CPU is 100 percent utilized, you should profile your application for performance improvements.

Minimize Impact of Bottlenecks

In this step, you tune your environment to minimize the impact of bottlenecks on your performance objectives. It is important to realize that in this step you are minimizing the impact of bottlenecks, not eliminating them. Tuning allows you to adjust resources to achieve your performance objectives. For the scope of this document, this includes (from most important to least important):

- Tune Your Application

- Tune your DB

- Tune WebLogic Server Performance Parameters

- Tune Your JVM

- Tune the Operating System

- Tuning the WebLogic Persistent Store

Tune Your Application

To quote the authors of Oracle WebLogic Server: Optimizing WebLogic Server Performance: "Good application performance starts with good application design. Overly-complex or poorly-designed applications will perform poorly regardless of the system-level tuning and best practices employed to improve performance." In other words, a poorly designed application can create unnecessary bottlenecks. For example, resource contention could be a case of poor design, rather than inherent to the application domain.

For more information, see:

- Chapter 10, "Tuning WebLogic Server EJBs"

- Chapter 11, "Tuning Message-Driven Beans"

- Chapter 12, "Tuning Data Sources"

- Chapter 13, "Tuning Transactions"

- Chapter 14, "Tuning WebLogic JMS"

- Chapter 15, "Tuning WebLogic JMS Store-and-Forward"

- Chapter 16, "Tuning WebLogic Message Bridge"

- Chapter 17, "Tuning Resource Adapters"

- Chapter 18, "Tuning Web Applications"

- Chapter 19, "Tuning Web Services"

- Chapter 20, "Tuning WebLogic Tuxedo Connector"

Tune your DB

Your database can be a major enterprise-level bottleneck. Database optimization can be complex and vender dependent. See DataBase Tuning.

Tune WebLogic Server Performance Parameters

The WebLogic Server uses a number of OOTB (out-of-the-box) performance-related parameters that can be fine-tuned depending on your environment and applications. Tuning these parameters based on your system requirements (rather than running with default settings) can greatly improve both single-node performance and the scalability characteristics of an application. See Chapter 7, "Tuning WebLogic Server".

Tune Your JVM

The Java virtual machine (JVM) is a virtual "execution engine" instance that executes the bytecodes in Java class files on a microprocessor. See Chapter 5, "Tuning Java Virtual Machines (JVMs)".

Tune the Operating System

Each operating system sets default tuning parameters differently. For Windows platforms, the default settings are usually sufficient. However, the UNIX and Linux operating systems usually need to be tuned appropriately. See Chapter 4, "Operating System Tuning".

Achieve Performance Objectives

Performance tuning is an iterative process. After you have minimized the impact of bottlenecks on your system, go to Step 2, Measure Your Performance Metrics and determine if you have met your performance objectives.

Tuning Tips

This section provides tips and guidelines when tuning overall system performance:

- Performance tuning is not a silver bullet. Simply put, good system performance depends on: good design, good implementation, defined performance objectives, and performance tuning.

- Performance tuning is ongoing process. Implement mechanisms that provide performance metrics which you can compare against your performance objectives, allowing you to schedule a tuning phase before your system fails.

- The object is to meet your performance objectives, not eliminate all bottlenecks. Resources within a system are finite. By definition, at least one resource (CPU, memory, or I/O) will be a bottleneck in the system. Tuning allows you minimize the impact of bottlenecks on your performance objectives.

- Design your applications with performance in mind:

- Keep things simple - avoid inappropriate use of published patterns.

- Apply Java EE performance patterns.

- Optimize your Java code.

4 Operating System Tuning

This chapter describes how to tune your operating system. Proper OS tuning improves system performance by preventing the occurrence of error conditions. Operating system error conditions always degrade performance. Typically most error conditions are TCP tuning parameter related and are caused by the operating system's failure to release old sockets from a close_wait call. Common errors are "connection refused", "too many open files" on the server-side, and "address in use: connect" on the client-side.

In most cases, these errors can be prevented by adjusting the TCP wait_time value and the TCP queue size. Although users often find the need to make adjustments when using tunnelling, OS tuning may be necessary for any protocol under sufficiently heavy loads.

Tune your operating system according to your operating system documentation. For Windows platforms, the default settings are usually sufficient. However, the Solaris and Linux platforms usually need to be tuned appropriately.

5 Tuning Java Virtual Machines (JVMs)

This chapter describes how to configure JVM tuning options for WebLogic Server. The Java virtual machine (JVM) is a virtual "execution engine" instance that executes the bytecodes in Java class files on a microprocessor. How you tune your JVM affects the performance of WebLogic Server and your applications.

- JVM Tuning Considerations

- Which JVM for Your System?

- Garbage Collection

- Enable Spinning for IA32 Platforms

JVM Tuning Considerations

The following table presents general JVM tuning considerations for WebLogic Server.

Table 5-1 General JVM Tuning Considerations

Tuning Factor

Information Reference

JVM vendor and version

Use only production JVMs on which WebLogic Server has been certified. This release of WebLogic Server supports only those JVMs that are Java SE 5.0-compliant.

See "Supported Configurations" in What's New in Oracle WebLogic Server for links to the latest certification information on various platforms.

Tuning heap size and garbage collection

For WebLogic Server heap size tuning details, see Garbage Collection.

Choosing a GC (garbage collection) scheme

Depending on your application, there are a number of GC schemes available for managing your system memory, as described in Choosing a Garbage Collection Scheme.

Mixed client/server JVMs

Deployments using different JVM versions for the client and server are supported in WebLogic Server. See "Supported Configurations" in What's New in Oracle WebLogic Server for links to the latest supported mixed client/server JVMs.

UNIX threading models

Choices you make about Solaris threading models can have a large impact on the performance of your JVM on Solaris. You can choose from multiple threading models and different methods of synchronization within the model, but this varies from JVM to JVM.

See "Performance Documentation For the Java Hotspot Virtual Machine: Threading" at http://java.sun.com/docs/hotspot/threads/threads.html.

Which JVM for Your System?

Although this section focuses on the Java SE 5.0 JVM for the Windows, UNIX, and Linux platforms, the JRockit JVM was developed expressly for server-side applications and optimized for Intel architectures to ensure reliability, scalability, manageability, and flexibility for Java applications. For more information about the benefits of using JRockit on Windows and Linux platforms, see "Introduction to JRockit JDK" at http://docs.oracle.com/docs/cd/E13150_01/jrockit_jvm/jrockit/webdocs/index.html.

For more information on JVMs in general, see "Introduction to the JVM specification" at http://java.sun.com/docs/books/vmspec/2nd-edition/html/Introduction.doc.html#3057.

Changing To a Different JVM

When you create a domain, if you choose to customize the configuration, the Configuration Wizard presents a list of JDKs that WebLogic Server installed. From this list, you choose the JVM that you want to run your domain and the wizard configures the Oracle start scripts based on your choice. After you create a domain, if you want to use a different JVM, see "Changing the JVM That Runs Servers" in Managing Server Startup and Shutdown for Oracle WebLogic Server.

Garbage Collection

Garbage collection is the VM's process of freeing up unused Java objects in the Java heap. The following sections provide information on tuning your VM's garbage collection:

- VM Heap Size and Garbage Collection

- Choosing a Garbage Collection Scheme

- Using Verbose Garbage Collection to Determine Heap Size

- Specifying Heap Size Values

- Automatically Logging Low Memory Conditions

- Manually Requesting Garbage Collection

- Requesting Thread Stacks

VM Heap Size and Garbage Collection

The Java heap is where the objects of a Java program live. It is a repository for live objects, dead objects, and free memory. When an object can no longer be reached from any pointer in the running program, it is considered "garbage" and ready for collection. A best practice is to tune the time spent doing garbage collection to within 5% of execution time.

The JVM heap size determines how often and how long the VM spends collecting garbage. An acceptable rate for garbage collection is application-specific and should be adjusted after analyzing the actual time and frequency of garbage collections. If you set a large heap size, full garbage collection is slower, but it occurs less frequently. If you set your heap size in accordance with your memory needs, full garbage collection is faster, but occurs more frequently.

The goal of tuning your heap size is to minimize the time that your JVM spends doing garbage collection while maximizing the number of clients that WebLogic Server can handle at a given time. To ensure maximum performance during benchmarking, you might set high heap size values to ensure that garbage collection does not occur during the entire run of the benchmark.

You might see the following Java error if you are running out of heap space:

java.lang.OutOfMemoryError <<no stack trace available>>
java.lang.OutOfMemoryError <<no stack trace available>>
Exception in thread "main"

To modify heap space values, see Specifying Heap Size Values.

To configure WebLogic Server to detect automatically when you are running out of heap space and to address low memory conditions in the server, see Automatically Logging Low Memory Conditions and Specifying Heap Size Values.

Choosing a Garbage Collection Scheme

Depending on which JVM you are using, you can choose from several garbage collection schemes to manage your system memory. For example, some garbage collection schemes are more appropriate for a given type of application. Once you have an understanding of the workload of the application and the different garbage collection algorithms utilized by the JVM, you can optimize the configuration of the garbage collection.

Refer to the following links for in-depth discussions of garbage collection options for your JVM:

- For an overview of the garbage collection schemes available with Sun's HotSpot VM, see "Tuning Garbage Collection with the 5.0 Java Virtual Machine" at http://www.oracle.com/technetwork/java/gc-tuning-5-138395.html.

- For a comprehensive explanation of the collection schemes available, see "Improving Java Application Performance and Scalability by Reducing Garbage Collection Times and Sizing Memory Using JDK 1.4.1" at http://www.oracle.com/technetwork/java/index-jsp-138820.html.

- For a discussion of the garbage collection schemes available with the JRockit JDK, see "Using the JRockt Memory Management System" at http://www.oracle.com/technetwork/middleware/jrockit/overview/index.html.

- For some pointers about garbage collection from an HP perspective, see "Performance tuning Java: Tuning steps" at http://h21007.www2.hp.com/dspp/tech/tech_TechDocumentDetailPage_IDX/1,1701,1604,00.html.

Using Verbose Garbage Collection to Determine Heap Size

The verbose garbage collection option (verbosegc) enables you to measure exactly how much time and resources are put into garbage collection. To determine the most effective heap size, turn on verbose garbage collection and redirect the output to a log file for diagnostic purposes.

The following steps outline this procedure:

1. Monitor the performance of WebLogic Server under maximum load while running your application.

2. Use the -verbosegc option to turn on verbose garbage collection output for your JVM and redirect both the standard error and standard output to a log file.
This places thread dump information in the proper context with WebLogic Server informational and error messages, and provides a more useful log for diagnostic purposes.

For example, on Windows and Solaris, enter the following:

% java -ms32m -mx200m -verbosegc -classpath $CLASSPATH
-Dweblogic.Name=%SERVER_NAME% -Dbea.home="C:\Oracle\Middleware"
-Dweblogic.management.username=%WLS_USER%
-Dweblogic.management.password=%WLS_PW%
-Dweblogic.management.server=%ADMIN_URL%
-Dweblogic.ProductionModeEnabled=%STARTMODE%
-Djava.security.policy="%WL_HOME%\server\lib\weblogic.policy" weblogic.Server >> logfile.txt 2>&1

where the logfile.txt 2>&1 command redirects both the standard error and standard output to a log file.

On HPUX, use the following option to redirect stderr stdout to a single file:

-Xverbosegc:file=/tmp/gc$$.out

where $$ maps to the process ID (PID) of the Java process. Because the output includes timestamps for when garbage collection ran, you can infer how often garbage collection occurs.

3. Analyze the following data points:

1. How often is garbage collection taking place? In the weblogic.log file, compare the time stamps around the garbage collection.

2. How long is garbage collection taking? Full garbage collection should not take longer than 3 to 5 seconds.

3. What is your average memory footprint? In other words, what does the heap settle back down to after each full garbage collection? If the heap always settles to 85 percent free, you might set the heap size smaller.

4. Review the New generation heap sizes (Sun) or Nursery size (Jrockit).

- For Jrockit: see JRockit JVM Heap Size Options.

- For Sun: see Java HotSpot VM Heap Size Options.

5. Make sure that the heap size is not larger than the available free RAM on your system.
Use as large a heap size as possible without causing your system to "swap" pages to disk. The amount of free RAM on your system depends on your hardware configuration and the memory requirements of running processes on your machine. See your system administrator for help in determining the amount of free RAM on your system.

6. If you find that your system is spending too much time collecting garbage (your allocated virtual memory is more than your RAM can handle), lower your heap size.
Typically, you should use 80 percent of the available RAM (not taken by the operating system or other processes) for your JVM.

7. If you find that you have a large amount of available free RAM remaining, run more instances of WebLogic Server on your machine.
Remember, the goal of tuning your heap size is to minimize the time that your JVM spends doing garbage collection while maximizing the number of clients that WebLogic Server can handle at a given time.

JVM vendors may provide other options to print comprehensive garbage collection reports. For example, you can use the JRockit JVM -Xgcreport option to print a comprehensive garbage collection report at program completion, see "Viewing Garbage Collection Behavior", at http://docs.oracle.com/docs/cd/E13150_01/jrockit_jvm/jrockit/webdocs/index.html.

Specifying Heap Size Values

System performance is greatly influenced by the size of the Java heap available to the JVM. This section describes the command line options you use to define the heap sizes values.You must specify Java heap size values each time you start an instance of WebLogic Server. This can be done either from the java command line or by modifying the default values in the sample startup scripts that are provided with the WebLogic distribution for starting WebLogic Server.

- Tuning Tips for Heap Sizes

- JRockit JVM Heap Size Options

- Java HotSpot VM Heap Size Options

Tuning Tips for Heap Sizes

The following section provides general guidelines for tuning VM heap sizes:

- The heap sizes should be set to values such that the maximum amount of memory used by the VM does not exceed the amount of available physical RAM. If this value is exceeded, the OS starts paging and performance degrades significantly. The VM always uses more memory than the heap size. The memory required for internal VM functionality, native libraries outside of the VM, and permanent generation memory (for the Sun VM only: memory required to store classes and methods) is allocated in addition to the heap size settings.

- When using a generational garbage collection scheme, the nursery size should not exceed more than half the total Java heap size. Typically, 25% to 40% of the heap size is adequate.

- In production environments, set the minimum heap size and the maximum heap size to the same value to prevent wasting VM resources used to constantly grow and shrink the heap. This also applies to the New generation heap sizes (Sun) or Nursery size (Jrockit).

JRockit JVM Heap Size Options

Although JRockit provides automatic heap resizing heuristics, they are not optimal for all applications. In most situations, best performance is achieved by tuning the VM for each application by adjusting the heaps size options shown in the following table.

Table 5-2 JRockit JVM Heap Size Options

TASK

Option

Description

Setting the Nursery

-Xns

Optimally, you should try to make the nursery as large as possible while still keeping the garbage collection pause times acceptably low. This is particularly important if your application is creating a lot of temporary objects.

The maximum size of a nursery cannot exceed 95% of the maximum heap size.

Setting initial and minimum heap size

-Xms

Oracle recommends setting the minimum heap size (-Xms) equal to the maximum heap size (-Xmx) to minimize garbage collections.

Setting maximum heap size

-Xmx

Setting a low maximum heap value compared to the amount of live data decrease performance by forcing frequent garbage collections.

Setting garbage collection

-Xgc: parallel

Performs adaptive optimizations as early as possible in the Java application run.

-XXaggressive:memory

To do this, the bottleneck detector will run with a higher frequency from the start and then gradually lower its frequency. This options also tells JRockit to use the available memory aggressively.

For example, when you start a WebLogic Server instance from a java command line, you could specify the JRockit VM heap size values as follows:

$ java -Xns10m -Xms512m -Xmx512m

The default size for these values is measured in bytes. Append the letter 'k' or 'K' to the value to indicate kilobytes, 'm' or 'M' to indicate megabytes, and 'g' or 'G' to indicate gigabytes. The example above allocates 10 megabytes of memory to the Nursery heap sizes and 512 megabytes of memory to the minimum and maximum heap sizes for the WebLogic Server instance running in the JVM.

For detailed information about setting the appropriate heap sizes for WebLogic's JRockit JVM, see "Tuning the JRockit JVM" at http://docs.oracle.com/docs/cd/E13150_01/jrockit_jvm/jrockit/webdocs/index.html.

Other JRockit VM Options

Oracle provides other command-line options to improve the performance of your JRockit VM. For detailed information, see "Command Line Reference " at http://docs.oracle.com/docs/cd/E13150_01/jrockit_jvm/jrockit/jrdocs/refman/index.html.

Java HotSpot VM Heap Size Options

You achieve best performance by individually tuning each application. However, configuring the Java HotSpot VM heap size options listed in the following table when starting WebLogic Server increases performance for most applications.

These options may differ depending on your architecture and operating system. See your vendor's documentation for platform-specific JVM tuning options.

Table 5-3 Java Heap Size Options

Task

Option

Comments

Setting the New generation heap size

-XX:NewSize

As a general rule, set -XX:NewSize to be one-fourth the size of the heap size. Increase the value of this option for larger numbers of short-lived objects.

Be sure to increase the New generation as you increase the number of processors. Memory allocation can be parallel, but garbage collection is not parallel.

Setting the maximum New generation heap size

-XX:MaxNewSize

Set the maximum size of the New Generation heap size.

Setting New heap size ratios

-XX:SurvivorRatio

The New generation area is divided into three sub-areas: Eden, and two survivor spaces that are equal in size.

Configure the ratio of the Eden/survivor space size. Try setting this value to 8, and then monitor your garbage collection.

Setting initial heap size

-Xms

As a general rule, set intial heap size (-Xms) equal to the maximum heap size (-Xmx) to minimize garbage collections.

Setting maximum heap size

-Xmx

Set the maximum size of the heap.

Setting Big Heaps and Intimate Shared Memory

-XX:+UseISM -XX:+AggressiveHeap

See http://java.sun.com/docs/hotspot/ism.html

For example, when you start a WebLogic Server instance from a java command line, you could specify the HotSpot VM heap size values as follows:

$ java -XX:NewSize=128m -XX:MaxNewSize=128m -XX:SurvivorRatio=8 -Xms512m -Xmx512m

The default size for these values is measured in bytes. Append the letter 'k' or 'K' to the value to indicate kilobytes, 'm' or 'M' to indicate megabytes, and 'g' or 'G' to indicate gigabytes. The example above allocates 128 megabytes of memory to the New generation and maximum New generation heap sizes, and 512 megabytes of memory to the minimum and maximum heap sizes for the WebLogic Server instance running in the JVM.

Other Java HotSpot VM Options

Oracle provides other standard and non-standard command-line options to improve the performance of your VM. How you use these options depends on how your application is coded.

Test both your client and server JVMs to see which options perform better for your particular application. See http://www.oracle.com/technetwork/java/javase/tech/vmoptions-jsp-140102.html for more information on the command-line options and environment variables that can affect the performance characteristics of the Java HotSpot Virtual Machine.

For additional examples of the HotSpot VM options, see:

- "Standard Options for Windows (Win32) VMs" at http://docs.oracle.com/javase/6/docs/technotes/tools/windows/java.html.

- "Standard Options for Solaris VMs and Linux VMs" at http://docs.oracle.com/javase/6/docs/technotes/tools/solaris/java.html.

The Java Virtual Machine document provides a detailed discussion of the Client and Server implementations of the Java virtual machine for Java SE 5.0 at http://docs.oracle.com/javase/1.5.0/docs/guide/vm/index.html.

Automatically Logging Low Memory Conditions

WebLogic Server enables you to automatically log low memory conditions observed by the server. WebLogic Server detects low memory by sampling the available free memory a set number of times during a time interval. At the end of each interval, an average of the free memory is recorded and compared to the average obtained at the next interval. If the average drops by a user-configured amount after any sample interval, the server logs a low memory warning message in the log file and sets the server health state to "warning." See "Log low memory conditions" in Oracle WebLogic Server Administration Console Help.

Manually Requesting Garbage Collection

You may find it necessary to manually request full garbage collection from the Administration Console. When you do, remember that garbage collection is costly as the JVM often examines every living object in the heap. See "Manually request garbage collection" in Oracle WebLogic Server Administration Console Help.

Requesting Thread Stacks

You may find it necessary to display thread stacks while tuning your applications. See "Display thread stacks" in Oracle WebLogic Server Administration Console Help.

Enable Spinning for IA32 Platforms

If you are running a high-stress application with heavily contended locks on a multiprocessor system, you can attempt to improve performance by using spinning. This option enables the ability to spin the lock for a short time before going to sleep.

Sun JDK

Sun has changed the default lock spinning behavior in JDK 5.0 on the Windows IA32 platform. For the JDK 5.0 release, lock spinning is disabled by default. For this release, Oracle has explicitly enabled spinning in the environment scripts used to start WebLogic Server. To enable spinning, use the following VM option:

-XX:+UseSpinning

JRockit

The JRockit VM automatically adjusts the spinning for different locks, eliminating the need set this parameter.

6 Tuning WebLogic Diagnostic Framework and JRockit Flight Recorder Integration

This chapter provides information on how to tune WLDF integration with JRockit Mission Control Flight Recorder: WebLogic Diagnostic Framework (WLDF) provides specific integration points with JRockit Mission Control Flight Recorder. WebLogic Server events are propagated to the Flight Recorder for inclusion in a common data set for runtime or post-incident analysis. See "Using WLDF with Oracle JRockit Flight Recorder" in Configuring and Using the Diagnostics Framework for Oracle WebLogic Server.

- Using JRockit Flight Recorder

- Using WLDF

- Chapter 6, "Tuning Considerations"

Using JRockit Flight Recorder

The version of Oracle JRockit that is provided with WebLogic Server includes a component called JRockit Flight Recorder (JFR), a performance monitoring and profiling tool that provides configuration options for controlling the events generated by the JVM. For more information about JFR, see "Introduction to the Flight Recorder" in Oracle JRockit JRockit Flight Recorder Run Time Guide.

You can enable JFR at runtime to take JRA recordings from the JRockit Management Console. You also have the option of turning off the JFR and recordings at the JRockit JVM level from the java command line using:

$ java -XX:-FlightRecorder

Note:

If you use the -XX:-FlightRecorder option to disable JFR, it disables all JRA support, including the ability to turn on JRA at runtime.

Using WLDF

WLDF provides the Diagnostic Volume attribute to set the amount of code coverage that is enabled and the amount of data provided in the events that are generated for the covered code. The volume can be adjusted using the WebLogic Console, see "Configure WLDF diagnostic volume" in Oracle WebLogic Server Administration Console Help. You can also set the volume using WLST. The following code example sets the volume to Medium:

. . .
connect()
edit()
startEdit()
cd("Servers/myserver")
cd("ServerDiagnosticConfig")
cd("myserver")
cmo.setWLDFDiagnosticVolume("Medium")
save()
activate()
. . .

JRockit and WLDF generate global events that contain information about the recording settings even when disabled. For example, JVM Metadata events list active recordings and WLDF GlobalInformationEvents list the domain, server, machine, and volume level. You can use WLDF Image capture to capture JFR recordings along with other component information from WebLogic Server, such as configuration.

The Diagnostic Volume setting does not affect explicitly configured diagnostic modules. By default, the Diagnostic Volume is set to Low. By default the JRockit default recording is also Off. Setting the WLDF volume to Low or higher enables WLDF event generation and the JVM events which would have been included by default if the JRockit default recording were enabled separately. So if you turn the WLDF volume to Low, Medium, or High, you get WLDF events and JVM events recorded in the JFR, there is no need to separately enable the JRockit default recording.

Using JRockit controls outside of WLDF to control the default JVM recording

You can enable the JVM default recording (or another recording) and continue to generate JVM events regardless of the WLDF volume setting. This allows you to continue to generate JVM events when WLDF events are off.

Tuning Considerations

In most environments, there is little performance impact when the Diagnostic Volume is set to Low and the most performance impact if Diagnostic Volume is set to High. The volume of diagnostic data produced by WebLogic Server needs to be weighed against potential performance loss.

Note:

There is a known issue that can cause a potentially large set of JVM events to be generated when WLDF captures the JFR data to the image capture. The events generated are at the same timestamp as the WLDF image capture and are mostly large numbers of JIT compilation events. With the default JFR and WLDF settings, these events are seen only during the WLDF image capture can be ignored. The expectation is that the VM events generating during Diagnostic Image capture should have little performance impact, as they are generated in a short window and are disabled during normal operation.

7 Tuning WebLogic Server

This chapter describes how to tune WebLogic Server to match your application needs.

- Setting Java Parameters for Starting WebLogic Server

- Development vs. Production Mode Default Tuning Values

- Thread Management

- Tuning Network I/O

- Setting Your Compiler Options

- Using WebLogic Server Clusters to Improve Performance

- Monitoring a WebLogic Server Domain

- Tuning Class and Resource Loading

- Server Migration with Database Leasing on RAC Clusters

Setting Java Parameters for Starting WebLogic Server

Java parameters must be specified whenever you start WebLogic Server. For simple invocations, this can be done from the command line with the weblogic.Server command. However, because the arguments needed to start WebLogic Server from the command line can be lengthy and prone to error, Oracle recommends that you incorporate the command into a script. To simply this process, you can modify the default values in the sample scripts that are provided with the WebLogic distribution to start WebLogic Server, as described in "Specifying Java Options for a WebLogic Server Instance" in Managing Server Startup and Shutdown for Oracle WebLogic Server.

If you used the Configuration Wizard to create your domain, the WebLogic startup scripts are located in the domain-name directory where you specified your domain. By default, this directory is MW_HOME\user_projects\domain\domain-name, where MW_HOME is the Middleware Home directory containing the Oracle product installation, and domain-name is the name of the domain directory defined by the selected configuration template.

You need to modify some default Java values in these scripts to fit your environment and applications. The important performance tuning parameters in these files are the JAVA_HOME parameter and the Java heap size parameters:

- Change the value of the variable JAVA_HOME to the location of your JDK. For example:

set JAVA_HOME=C:\Oracle\Middleware\jdk160_11

- For higher performance throughput, set the minimum java heap size equal to the maximum heap size. For example:

"%JAVA_HOME%\bin\java" -server –Xms512m –Xmx512m -classpath %CLASSPATH% -

See Specifying Heap Size Values for details about setting heap size options.

Development vs. Production Mode Default Tuning Values

You can indicate whether a domain is to be used in a development environment or a production environment. WebLogic Server uses different default values for various services depending on the type of environment you specify. Specify the startup mode for your domain as shown in the following table.

Table 7-1 Startup Modes

Choose this mode

when . . .

Development

You are creating your applications. In this mode, the configuration of security is relatively relaxed, allowing you to auto-deploy applications.

Production

Your application is running in its final form. In this mode, security is fully configured.

The following table lists the performance-related configuration parameters that differ when switching from development to production startup mode.

Table 7-2 Differences Between Development and Production Modes

Tuning Parameter

In development mode . . .

In production mode . . .

SSL

You can use the demonstration digital certificates and the demonstration keystores provided by the WebLogic Server security services. With these certificates, you can design your application to work within environments secured by SSL.

For more information about managing security, see "Configuring SSL" in Securing WebLogic Server.

You should not use the demonstration digital certificates and the demonstration keystores. If you do so, a warning message is displayed.

Deploying Applications

WebLogic Server instances can automatically deploy and update applications that reside in the domain_name/autodeploy directory (where domain_name is the name of a domain).

It is recommended that this method be used only in a single-server development environment.

For more information, see "Auto-Deploying Applications in Development Domains" in Deploying Applications to Oracle WebLogic Server.

The auto-deployment feature is disabled, so you must use the WebLogic Server Administration Console, the weblogic.Deployer tool, or the WebLogic Scripting Tool (WLST). For more information, see "Understanding WebLogic Server Deployment" in Deploying Applications to Oracle WebLogic Server.

For information on switching the startup mode from development to production, see "Change to Production Mode" in the Oracle WebLogic Server Administration Console Help.

Deployment

The following sections provide information on how to improve deployment performance:

- On-demand Deployment of Internal Applications

- Use FastSwap Deployment to Minimize Redeployment Time

- Generic Overrides

On-demand Deployment of Internal Applications

WebLogic Server deploys many internal applications during startup. Many of these internal applications are not needed by every user. You can configure WebLogic Server to wait and deploy these applications on the first access (on-demand) instead of always deploying them during server startup. This can conserve memory and CPU time during deployment as well as improving startup time and decreasing the base memory footprint for the server.For a development domain, the default is for WLS to deploy internal applications on-demand. For a production-mode domain, the default is for WLS to deploy internal applications as part of server startup. For more information on how to use and configure this feature, see On-demand Deployment of Internal Applications in Deploying Applications to Oracle WebLogic Server.

Use FastSwap Deployment to Minimize Redeployment Time

In deployment mode, you can set WebLogic Server to redefine Java classes in-place without reloading the ClassLoader. This means that you do not have to wait for an application to redeploy and then navigate back to wherever you were in the Web page flow. Instead, you can make your changes, auto compile, and then see the effects immediately. For more information on how to use and configure this feature, see Using FastSwap Deployment to Minimize Redeployment in Deploying Applications to WebLogic Server.

Generic Overrides

Generic overrides allow you to override application specific property files without having to crack a jar file by placing application specific files to be overridden into the AppFileOverrides optional subdirectory. For more information on how to use and configure this feature, see Generic File Loading Overrides in Deploying Applications to WebLogic Server.

Thread Management

WebLogic Server provides the following mechanisms to manage threads to perform work.

- Tuning a Work Manager

- Tuning Execute Queues

- Understanding the Differences Between Work Managers and Execute Queues

- Tuning the Stuck Thread Detection Behavior

Tuning a Work Manager

In this release, WebLogic Server allows you to configure how your application prioritizes the execution of its work. Based on rules you define and by monitoring actual runtime performance, WebLogic Server can optimize the performance of your application and maintain service level agreements (SLA).

You tune the thread utilization of a server instance by defining rules and constraints for your application by defining a Work Manger and applying it either globally to WebLogic Server domain or to a specific application component. The primary tuning considerations are:

- How Many Work Managers are Needed?

- What are the SLA Requirements for Each Work Manager?

See "Using Work Managers to Optimize Scheduled Work" in Configuring Server Environments for Oracle WebLogic Server.

How Many Work Managers are Needed?

Each distinct SLA requirement needs a unique work manager.

What are the SLA Requirements for Each Work Manager?

Service level agreement (SLA) requirements are defined by instances of request classes. A request class expresses a scheduling guideline that a server instance uses to allocate threads. See "Understanding Work Managers" in Configuring Server Environments for Oracle WebLogic Server.

Tuning Execute Queues

In previous versions of WebLogic Server, processing was performed in multiple execute queues. Different classes of work were executed in different queues, based on priority and ordering requirements, and to avoid deadlocks. See Appendix A, "Using the WebLogic 8.1 Thread Pool Model.".

Note:

Oracle recommends migrating applications to use work managers.

Understanding the Differences Between Work Managers and Execute Queues

The easiest way to conceptually visualize the difference between the execute queues of previous releases with work managers is to correlate execute queues (or rather, execute-queue managers) with work managers and decouple the one-to-one relationship between execute queues and thread-pools.

For releases prior to WebLogic Server 9.0, incoming requests are put into a default execute queue or a user-defined execute queue. Each execute queue has an associated execute queue manager that controls an exclusive, dedicated thread-pool with a fixed number of threads in it. Requests are added to the queue on a first-come-first-served basis. The execute-queue manager then picks the first request from the queue and an available thread from the associated thread-pool and dispatches the request to be executed by that thread.

For releases of WebLogic Server 9.0 and higher, there is a single priority-based execute queue in the server. Incoming requests are assigned an internal priority based on the configuration of work managers you create to manage the work performed by your applications. The server increases or decreases threads available for the execute queue depending on the demand from the various work-managers. The position of a request in the execute queue is determined by its internal priority:

- The higher the priority, closer it is placed to the head of the execute queue.

- The closer to the head of the queue, more quickly the request will be dispatched a thread to use.

Work managers provide you the ability to better control thread utilization (server performance) than execute-queues, primarily due to the many ways that you can specify scheduling guidelines for the priority-based thread pool. These scheduling guidelines can be set either as numeric values or as the capacity of a server-managed resource, like a JDBC connection pool.

Migrating from Previous Releases

If you upgrade application domains from prior releases that contain execute queues, the resulting 9.x domain will contain execute queues.

- Migrating application domains from a previous release to WebLogic Server 9.x does not automatically convert an execute queues to work manager.

- If execute queues are present in the upgraded application configuration, the server instance assigns work requests appropriately to the execute queue specified in the dispatch-policy.

- Requests without a dispatch-policy use the self-tuning thread pool.

See "Roadmap for Upgrading Your Application Environment" in Upgrade Guide for Oracle WebLogic Server.

Tuning the Stuck Thread Detection Behavior

WebLogic Server automatically detects when a thread in an execute queue becomes "stuck." Because a stuck thread cannot complete its current work or accept new work, the server logs a message each time it diagnoses a stuck thread.

WebLogic Server diagnoses a thread as stuck if it is continually working (not idle) for a set period of time. You can tune a server's thread detection behavior by changing the length of time before a thread is diagnosed as stuck, and by changing the frequency with which the server checks for stuck threads. Although you can change the criteria WebLogic Server uses to determine whether a thread is stuck, you cannot change the default behavior of setting the "warning" and "critical" health states when all threads in a particular execute queue become stuck. For more information, see "Configuring WebLogic Server to Avoid Overload Conditions" in Configuring Server Environments for Oracle WebLogic Server. To configure stuck thread detection behavior, see "Tuning execute thread detection behavior" in Oracle WebLogic Server Administration Console Help.

Tuning Network I/O

The following sections provide information on network communication between clients and servers (including T3 and IIOP protocols, and their secure versions):

- Tuning Muxers

- Which Platforms Have Performance Packs?

- Enabling Performance Packs

- Changing the Number of Available Socket Readers

- Network Channels

- Reducing the Potential for Denial of Service Attacks

- Tune the Chunk Parameters

- Tuning Connection Backlog Buffering

- Tuning Cached Connections

Tuning Muxers

WebLogic Server uses software modules called muxers to read incoming requests on the server and incoming responses on the client. WebLogic Server supports the following muxers:

- Java Muxer

- Native Muxers

- Non-Blocking IO Muxer

WebLogic Server selects which muxer implementation is using the following criteria:

- If the Muxer Class attribute is set to weblogic.socket.NIOSocketMuxer or -Dweblogic.MuxerClass=weblogic.socket.NIOSocketMuxer flag is set, the NIOSocketMuxer is used.

- If NativeIOEnabled is false and MuxerClass is null, the Java Socket Muxer is used.

- If NativeIOEnabled is true and MuxerClass is null, native muxers are used, if available for your platform.

Client applications use the Java socket muxer.

Java Muxer

A Java muxer has the following characteristics:

- Uses pure Java to read data from sockets.

- It is also the only muxer available for RMI clients.

- Blocks on reads until there is data to be read from a socket. This behavior does not scale well when there are a large number of sockets and/or when data arrives infrequently at sockets. This is typically not an issue for clients, but it can create a huge bottleneck for a server.

If the Enable Native IO parameter is not selected, the server instance exclusively uses the Java muxer. This maybe acceptable if there are a small number of clients and the rate at which requests arrive at the server is fairly high. Under these conditions, the Java muxer performs as well as a native muxer and eliminate Java Native Interface (JNI) overhead. Unlike native muxers, the number of threads used to read requests is not fixed and is tunable for Java muxers by configuring the Percent Socket Readers parameter setting in the Administration Console. See Changing the Number of Available Socket Readers. Ideally, you should configure this parameter so the number of threads roughly equals the number of remote concurrently connected clients up to 50% of the total thread pool size. Each thread waits for a fixed amount of time for data to become available at a socket. If no data arrives, the thread moves to the next socket.

Native Muxers

Native muxers use platform-specific native binaries to read data from sockets. The majority of all platforms provide some mechanism to poll a socket for data. For example, Unix systems use the poll system call and the Windows architecture uses completion ports. Native muxers provide superior scalability because they implement a non-blocking thread model. When a native muxer is used, the server creates a fixed number of threads dedicated to reading incoming requests. Oracle recommends using the default setting of true for the Enable Native IO parameter which allows the server to automatically select the appropriate muxer to use. See "Enable native IO" in Oracle WebLogic Server Administration Console Help.

With native muxers, you may be able to improve throughput for some cpu-bound applications (for example, SpecJAppServer) by using the following:

-Dweblogic.socket.SocketMuxer.DELAY_POLL_WAKEUP=xx

where xx is the amount of time, in microseconds, to delay before checking if data is available. The default value is 0, which corresponds to no delay.

Non-Blocking IO Muxer

WebLogic Server provides a non-blocking IO implementation that may provide enhanced performance for some applications. See "Enable NIOSocketMuxer" in Oracle WebLogic Server Administration Console Help.

Note:

The Certicom SSL implementation is not supported with WebLogic Server's non-blocking IO implementation (weblogic.socket.NIOSocketMuxer). If you need to enable secure communication between applications, Oracle supports implementing JSSE (Java Secure Socket Extension). For more information, see "Secure Sockets Layer (SSL)" in Understanding Security for Oracle WebLogic Server.

Which Platforms Have Performance Packs?

Benchmarks show major performance improvements when you use native performance packs on machines that host WebLogic Server instances. Performance packs use a platform-optimized, native socket multiplexor to improve server performance. For example, the native socket reader multiplexor threads have their own execute queue and do not borrow threads from the default execute queue, which frees up default execute threads to do application work

To see which platforms currently have performance packs available:

1. See "Supported Configurations" in What's New in Oracle WebLogic Server to find links to the latest Certifications Pages.

2. Select your platform from the list of certified platforms.

3. Use your browser's Edit > Find to locate all instances of "Performance Pack" to verify whether it is included for the platform.

Enabling Performance Packs

The use of NATIVE performance packs are enabled by default in the configuration shipped with your distribution. You can use the Administration Console to verify that performance packs are enabled. See "Enable native IO" in Oracle WebLogic Server Administration Console Help.

Changing the Number of Available Socket Readers

If you must use the pure-Java socket reader implementation for host machines, you can improve the performance of socket communication by configuring the proper number of socket reader threads for each server instance and client machine. See "Tuning the number of available socket readers" in Oracle WebLogic Server Administration Console Help.

Network Channels

Network channels, also called network access points, allow you to specify different quality of service (QOS) parameters for network communication. Each network channel is associated with its own exclusive socket using a unique IP address and port. By default, requests from a multi-threaded client are multiplexed over the same remote connection and the server instance reads requests from the socket one at a time. If the request size is large, this becomes a bottleneck.

Although the primary role of a network channel is to control the network traffic for a server instance, you can leverage the ability to create multiple custom channels to allow a multi-threaded client to communicate with server instance over multiple connections, reducing the potential for a bottleneck. To configure custom multi-channel communication, use the following steps:

1. Configure multiple network channels using different IP and port settings. See "Configure custom network channels" in Oracle WebLogic Server Administration Console Help.

2. In your client-side code, use a JNDI URL pattern similar to the pattern used in clustered environments. The following is an example for a client using two network channels:

t3://<ip1>:<port1>,<ip2>:<port2>

See "Understanding Network Channels" in Configuring Server Environments for Oracle WebLogic Server.

Reducing the Potential for Denial of Service Attacks

To reduce the potential for Denial of Service (DoS) attacks while simultaneously optimizing system availability, WebLogic Server allows you to specify the following settings:

- Maximum incoming message size

- Complete message timeout

- Number of file descriptors (UNIX systems)

For optimal system performance, each of these settings should be appropriate for the particular system that hosts WebLogic Server and should be in balance with each other, as explained in the sections that follow.

Tuning Message Size

WebLogic Server allows you to specify a maximum incoming request size to prevent server from being bombarded by a series of large requests. You can set a global value or set specific values for different protocols and network channels. Although it does not directly impact performance, JMS applications that aggregate messages before sending to a destination may be refused if the aggregated size is greater than specified value. See "Servers: Protocols: General" in Oracle WebLogic Server Administration Console Help and Tuning Applications Using Unit-of-Order.

Tuning Complete Message Timeout

Make sure that the complete message timeout parameter is configured properly for your system. This parameter sets the maximum number of seconds that a server waits for a complete message to be received.

The default value is 60 seconds, which applies to all connection protocols for the default network channel. This setting might be appropriate if the server has a number of high-latency clients. However, you should tune this to the smallest possible value without compromising system availability.

If you need a complete message timeout setting for a specific protocol, you can alternatively configure a new network channel for that protocol.

For information about displaying the Administration Console page from which the complete message timeout parameter can be set, see "Configure protocols" in the Oracle WebLogic Server Administration Console Help.

Tuning Number of File Descriptors

On UNIX systems, each socket connection to WebLogic Server consumes a file descriptor. To optimize availability, the number of file descriptors for WebLogic Server should be appropriate for the host machine. By default, WebLogic Server configures 1024 file descriptors. However, this setting may be low, particularly for production systems.

Note that when you tune the number of file descriptors for WebLogic Server, your changes should be in balance with any changes made to the complete message timeout parameter. A higher complete message timeout setting results in a socket not closing until the message timeout occurs, which therefore results in a longer hold on the file descriptor. So if the complete message timeout setting is high, the file descriptor limit should also be set high. This balance provides optimal system availability with reduced potential for denial-of-service attacks.

For information about how to tune the number of available file descriptors, consult your UNIX vendor's documentation.

Tune the Chunk Parameters

A chunk is a unit of memory that the WebLogic Server network layer, both on the client and server side, uses to read data from and write data to sockets. To reduce memory allocation costs, a server instance maintains a pool of these chunks. For applications that handle large amounts of data per request, increasing the value on both the client and server sides can boost performance. The default chunk size is about 4K. Use the following properties to tune the chunk size and the chunk pool size:

- weblogic.Chunksize—Sets the size of a chunk (in bytes). The primary situation in which this may need to be increased is if request sizes are large. It should be set to values that are multiples of the network's maximum transfer unit (MTU), after subtracting from the value any Ethernet or TCP header sizes. Set this parameter to the same value on the client and server.

- weblogic.utils.io.chunkpoolsize—Sets the maximum size of the chunk pool. The default value is 2048. The value may need to be increased if the server starts to allocate and discard chunks in steady state. To determine if the value needs to be increased, monitor the CPU profile or use a memory/ heap profiler for call stacks invoking the constructor weblogic.utils.io.Chunk.

- weblogic.PartitionSize—Sets the number of pool partitions used (default is 4). The chunk pool can be a source of significant lock contention as each request to access to the pool must be synchronized. Partitioning the thread pool spreads the potential for contention over more than one partition.

Tuning Connection Backlog Buffering

You can tune the number of connection requests that a WebLogic Server instance will accept before refusing additional requests. The Accept Backlog parameter specifies how many Transmission Control Protocol (TCP) connections can be buffered in a wait queue. This fixed-size queue is populated with requests for connections that the TCP stack has received, but the application has not accepted yet. For more information on TCP tuning, see Operating System Tuning.

You can tune the number of connection requests that a WebLogic Server instance will accept before refusing additional requests, see "Tune connection backlog buffering" in Oracle WebLogic Server Administration Console Help.

Tuning Cached Connections

Use the http.keepAliveCache.socketHealthCheckTimeout system property for tuning the behavior of how a socket connection is returned from the cache when keep-alive is enabled when using HTTP 1.1 protocol. By default, the cache does not check the health condition before returning the cached connection to the client for use. Under some conditions, such as due to an unstable network connection, the system needs to check the connection's health condition before returning it to the client. To enable this behavior (checking the health condition), set http.keepAliveCache.socketHealthCheckTimeout to a value greater than 0.

Setting Your Compiler Options

You may improve performance by tuning your server's compiler options.

Compiling EJB Classes

Use the weblogic.appc utility to compile EJB container classes. If you compile Jar files for deployment into the EJB container, you must use weblogic.appc to generate the container classes. By default, ejbc uses the javac compiler. You may be able to improve performance by specifying a different compiler (such as IBM Jikes) using the -compiler flag or using the Administration console. For more information, see:

- "Implementing Enterprise Java Beans" in Programming WebLogic Enterprise JavaBeans for Oracle WebLogic Server.

- "Configure compiler options" in Oracle WebLogic Server Administration Console Help.

Setting JSP Compiler Options

The following sections provide information on tuning JSP compiler options:

- Precompile JSPs

- Optimize Java Expressions

Precompile JSPs

In the weblogic.xml file, the jsp-descriptor element defines parameter names and values for servlet JSPs. Use the precompile parameter to configure WebLogic Server to precompile your JSPs when WebLogic Server starts up. See the jsp-descriptor element in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server.

If you receive the following error message received when compiling JSP files on a UNIX machine:

failed: java.io.IOException: Not enough space

Try any or all of the following solutions:

- Add more RAM if you have only 256 MB.

- Raise the file descriptor limit, for example:

set rlim_fd_max = 4096
set rlim_fd_cur = 1024

Optimize Java Expressions

Set the optimize-java-expression element to optimize Java expressions to improve runtime performance. See jsp-descriptor in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server.

Using WebLogic Server Clusters to Improve Performance

A WebLogic Server cluster is a group of WebLogic Servers instances that together provide fail-over and replicated services to support scalable high-availability operations for clients within a domain. A cluster appears to its clients as a single server but is in fact a group of servers acting as one to provide increased scalability and reliability.

A domain can include multiple WebLogic Server clusters and non-clustered WebLogic Server instances. Clustered WebLogic Server instances within a domain behave similarly to non-clustered instances, except that they provide failover and load balancing. The Administration Server for the domain manages all the configuration parameters for the clustered and non-clustered instances.

For more information about clusters, see "Understanding WebLogic Server Clustering" in Using Clusters for Oracle WebLogic Server.

Scalability and High Availability

Scalability is the ability of a system to grow in one or more dimensions as more resources are added to the system. Typically, these dimensions include (among other things), the number of concurrent users that can be supported and the number of transactions that can be processed in a given unit of time.

Given a well-designed application, it is entirely possible to increase performance by simply adding more resources. To increase the load handling capabilities of WebLogic Server, add another WebLogic Server instance to your cluster—without changing your application. Clusters provide two key benefits that are not provided by a single server: scalability and availability.

WebLogic Server clusters bring scalability and high-availability to Java EE applications in a way that is transparent to application developers. Scalability expands the capacity of the middle tier beyond that of a single WebLogic Server or a single computer. The only limitation on cluster membership is that all WebLogic Servers must be able to communicate by IP multicast. New WebLogic Servers can be added to a cluster dynamically to increase capacity.

A WebLogic Server cluster guarantees high-availability by using the redundancy of multiple servers to insulate clients from failures. The same service can be provided on multiple servers in a cluster. If one server fails, another can take over. The ability to have a functioning server take over from a failed server increases the availability of the application to clients.

Note:

Provided that you have resolved all application and environment bottleneck issues, adding additional servers to a cluster should provide linear scalability. When doing benchmark or initial configuration test runs, isolate issues in a single server environment before moving to a clustered environment.

Clustering in the Messaging Service is provided through distributed destinations; connection concentrators, and connection load-balancing (determined by connection factory targeting); and clustered Store-and-Forward (SAF). Client load-balancing with respect to distributed destinations is tunable on connection factories. Distributed destination Message Driven Beans (MDBs) that are targeted to the same cluster that hosts the distributed destination automatically deploy only on cluster servers that host the distributed destination members and only process messages from their local destination. Distributed queue MDBs that are targeted to a different server or cluster than the host of the distributed destination automatically create consumers for every distributed destination member. For example, each running MDB has a consumer for each distributed destination queue member.

How to Ensure Scalability for WebLogic Clusters

In general, any operation that requires communication between the servers in a cluster is a potential scalability hindrance. The following sections provide information on issues that impact the ability to linearly scale clustered WebLogic servers:

- Database Bottlenecks

- Session Replication

- Asynchronous HTTP Session Replication

- Invalidation of Entity EJBs

- Invalidation of HTTP sessions

- JNDI Binding, Unbinding and Rebinding

Database Bottlenecks

In many cases where a cluster of WebLogic servers fails to scale, the database is the bottleneck. In such situations, the only solutions are to tune the database or reduce load on the database by exploring other options. See Chapter 9, "DataBase Tuning" and Chapter 12, "Tuning Data Sources".

Session Replication

User session data can be stored in two standard ways in a Java EE application: stateful session EJBs or HTTP sessions. By themselves, they are rarely a impact cluster scalability. However, when coupled with a session replication mechanism required to provide high-availability, bottlenecks are introduced. If a Java EE application has Web and EJB components, you should store user session data in HTTP sessions:

- HTTP session management provides more options for handling fail-over, such as replication, a shared DB or file.

- Superior scalability.

- Replication of the HTTP session state occurs outside of any transactions. Stateful session bean replication occurs in a transaction which is more resource intensive.

- The HTTP session replication mechanism is more sophisticated and provides optimizations a wider variety of situations than stateful session bean replication.

See Session Management.

Asynchronous HTTP Session Replication

Asynchronous replication of http sessions provides the option of choosing asynchronous session replication using:

- Asynchronous HTTP Session Replication using a Secondary Server

- Asynchronous HTTP Session Replication using a Database

Asynchronous HTTP Session Replication using a Secondary Server

Set the PersistentStoreType to async-replicated or async-replicated-if-clustered to specify asynchronous replication of data between a primary server and a secondary server. See session-descriptor section of Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server. To tune batched replication, adjust the SessionFlushThreshold parameter.

Replication behavior depends on cluster type. The following table describes how asynchronous replication occurs for a given cluster topology.

Table 7-3 Asynchronous Replication Behavior by Cluster Topology

Topology

Behavior

LAN

Replication to a secondary server within the same cluster occurs asynchronously with the "async-replication" setting in the webapp.

MAN

Replication to a secondary server in a remote cluster. This happens asynchronously with the "async-replication" setting in the webapp.

WAN

Replication to a secondary server within the cluster happens asynchronously with the "async-replication" setting in the webapp. Persistence to a database through a remote cluster happens asynchronously regardless of whether "async-replication" or "replication" is chosen.

The following section outlines asynchronous replication session behavior:

- During undeployment or redeployment:

- The session is unregistered and removed from the update queue.

- The session on the secondary server is unregistered.

- If the application is moved to admin mode, the sessions are flushed and replicated to the secondary server. If secondary server is down, the system attempts to failover to another server.

- A server shutdown or failure state triggers the replication of any batched sessions to minimize the potential loss of session information.

Asynchronous HTTP Session Replication using a Database

Set the PersistentStoreType to async-jdbc to specify asynchronous replication of data to a database. See session-descriptor section of Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server. To tune batched replication, adjust the SessionFlushThreshold and the SessionFlushInterval parameters.

The following section outlines asynchronous replication session behavior:

- During undeployment or redeployment:

- The session is unregistered and removed from the update queue.

- The session is removed from the database.

- If the application is moved to admin mode, the sessions are flushed and replicated to the database.

Invalidation of Entity EJBs

This applies to entity EJBs that use a concurrency strategy of Optimistic or ReadOnly with a read-write pattern.

Optimistic—When an Optimistic concurrency bean is updated, the EJB container sends a multicast message to other cluster members to invalidate their local copies of the bean. This is done to avoid optimistic concurrency exceptions being thrown by the other servers and hence the need to retry transactions. If updates to the EJBs are frequent, the work done by the servers to invalidate each other's local caches become a serious bottleneck. A flag called cluster-invalidation-disabled (default false) is used to turn off such invalidations. This is set in the rdbms descriptor file.

ReadOnly with a read-write pattern—In this pattern, persistent data that would otherwise be represented by a single EJB are actually represented by two EJBs: one read-only and the other updatable. When the state of the updateable bean changes, the container automatically invalidates corresponding read-only EJB instance. If updates to the EJBs are frequent, the work done by the servers to invalidate the read-only EJBs becomes a serious bottleneck.

Invalidation of HTTP sessions

Similar to Invalidation of Entity EJBs, HTTP sessions can also be invalidated. This is not as expensive as entity EJB invalidation, since only the session data stored in the secondary server needs to be invalidated. Oracle advises users to not invalidate sessions unless absolutely required.

JNDI Binding, Unbinding and Rebinding

In general, JNDI binds, unbinds and rebinds are expensive operations. However, these operations become a bigger bottleneck in clustered environments because JNDI tree changes have to be propagated to all members of a cluster. If such operations are performed too frequently, they can reduce cluster scalability significantly.

Running Multiple Server Instances on Multi-Core Machines

With multi-core machines, additional consideration must be given to the ratio of the number of available cores to clustered WebLogic Server instances. Because WebLogic Server has no built-in limit to the number of server instances that reside in a cluster, large, multi-core servers, can potentially host very large clusters or multiple clusters.

Consider the following when determining the optimal ratio of cores to WebLogic server instances:

- The memory requirements of the application. Choose the heap sizes of individual instance and the total number of instances to ensure that you're providing sufficient memory for the application and achieving good GC performance. For some applications, allocating very large heaps to a single instance may lead to longer GC pause times. In this case the performance may benefit from increasing the number of instances and giving each instance a smaller heap.

- Maximizing CPU utilization. While WebLogic Server is capable of utilizing multiple cores per instance, for some applications increasing the number of instances on a given machine (reducing the number of cores per instance) can improve CPU utilization and overall performance.

Monitoring a WebLogic Server Domain

The following sections provide information on how to monitor WebLogic Server domains:

- Using the Administration Console to Monitor WebLogic Server

- Using the WebLogic Diagnostic Framework

- Using JMX to Monitor WebLogic Server

- Using WLST to Monitor WebLogic Server

- Third-Party Tools to Monitor WebLogic Server

Using the Administration Console to Monitor WebLogic Server

The tool for monitoring the health and performance of your WebLogic Server domain is the Administration Console. See "Monitor servers" in Oracle WebLogic Server Administration Console Help.

Using the WebLogic Diagnostic Framework

The WebLogic Diagnostic Framework (WLDF) is a monitoring and diagnostic framework that defines and implements a set of services that run within WebLogic Server processes and participate in the standard server life cycle. See "Overview of the WLDF Architecture" in Configuring and Using the Diagnostics Framework for Oracle WebLogic Server.

Using JMX to Monitor WebLogic Server

WebLogic Server provides its own set of MBeans that you can use to configure, monitor, and manage WebLogic Server resources. See "Understanding WebLogic Server MBeans" in Developing Custom Management Utilities With JMX for Oracle WebLogic Server.

Using WLST to Monitor WebLogic Server

The WebLogic Scripting Tool (WLST) is a command-line scripting interface that system administrators and operators use to monitor and manage WebLogic Server instances and domains. See "Understanding WebLogic Server MBeans" in Developing Custom Management Utilities With JMX for Oracle WebLogic Server.

Resources to Monitor WebLogic Server

The Oracle Technology Network at http://www.oracle.com/technology/index.html provides product downloads, articles, sample code, product documentation, tutorials, white papers, news groups, and other key content for WebLogic Server.

Third-Party Tools to Monitor WebLogic Server

Oracle partners with other companies that provide production monitoring and management tools.

Tuning Class and Resource Loading

The default class and resource loading default behavior in WebLogic Server is to search the classloader hierarchy beginning with the root. As a result, the full system classpath is searched for every class or resource loading request, even if the class or resource belongs to the application. For classes and resources that are only looked up once (for example: classloading during deployment), the cost of the full classpath search is typically not a serious problem. For classes and resources that are requested repeatedly by an application at runtime (explicit application calls to loadClass or getResource) the CPU and memory overhead of repeatedly searching a long system and application classpath can be significant. The worst case scenario is when the requested class or resource is missing. A missing class or resource results in the cost of a full scan of the classpath and is compounded by the fact that if an application fails to find the class/resource it is likely to request it repeatedly. This problem is more common for resources than for classes.

Ideally, application code is optimized to avoid requests for missing classes and resources and frequent repeated calls to load the same class/resource. While it is not always possible to fix the application code (for example, a third party library), an alternative is to use WebLogic Server's "Filtering Loader Mechanism".

Filtering Loader Mechanism

WebLogic Server provides a filtering loader mechanism that allows the system classpath search to be bypassed when looking for specific application classes and resources that are on the application classpath. This mechanism requires a user configuration that specifies the specific classes and resources that bypass the system classpath search. See "Using a Filtering Classloader" in Developing Applications for Oracle WebLogic Server.

New for this release is the ability to filter resource loading requests. The basic configuration of resource filtering is specified in META-INF/weblogic-application.xml file and is similar to the class filtering. The the syntax for filtering resources is shown in the following example:

<prefer-application-resources>
<resource-name>x/y</resource-name>
<resource-name>z*</resource-name>
</prefer-application-resources>

In this example, resource filtering has been configured for the exact resource name "x/y" and for any resource whose name starts with "z". '*' is the only wild card pattern allowed. Resources with names matching these patterns are searched for only on the application classpath, the system classpath search is skipped.

Note:

If you add a class or resource to the filtering configuration and subsequently get exceptions indicating the class or resource isn't found, the most likely cause is that the class or resource is on the system classpath, not on the application classpath.

Class Caching

WebLogic Server allows you to enable class caching for faster start ups. Once you enable caching, the server records all the classes loaded until a specific criterion is reached and persists the class definitions in an invisible file. When the server restarts, the cache is checked for validity with the existing code sources and the server uses the cache file to bulk load the same sequence of classes recorded in the previous run. If any change is made to the system classpath or its contents, the cache will be invalidated and re-built on server restart.

The advantages of using class caching are:

- Reduces server startup time.

- The package level index reduces search time for all classes and resources.

For more information, see Configuring Class Caching in Developing Applications for Oracle WebLogic Server.

Note:

Class caching is supported in development mode when starting the server using a startWebLogic script. Class caching is disabled by default and is not supported in production mode. The decrease in startup time varies among different JRE vendors.

Server Migration with Database Leasing on RAC Clusters

When using server migration with database leasing on RAC Clusters, Oracle recommends synchronizing all RAC nodes in the environment. If the nodes are not synchronized, it is possible that a managed server that is renewing a lease will evaluate that the value of the clock on the RAC node is greater than the timeout value of leasing table. If it is more than 30 seconds, the server will fail and restart with the following log message:

<Mar 29, 2013 2:39:09 PM EDT> <Error> <Cluster> <BEA-000150> <Server failed
to get a connection to the database in the past 60 seconds for lease renewal.
Server will shut itself down.>

See "Configuring Time Synchronization for the Cluster" in the Oracle Grid Infrastructure Installation Guide.

8 Tuning the WebLogic Persistent Store

This chapter describes how to tune the persistent store, which provides a built-in, high-performance storage solution for WebLogic Server subsystems and services that require persistence.

- Overview of Persistent Stores

- Best Practices When Using Persistent Stores

- Tuning JDBC Stores

- Tuning File Stores

- Using a Network File System

Before reading this chapter, Oracle recommends becoming familiar with WebLogic store administration and monitoring. See Using the WebLogic Persistent Store in Configuring Server Environments for Oracle WebLogic Server.

Overview of Persistent Stores

The following sections provide information on using persistent stores.

- Using the Default Persistent Store

- Using Custom File Stores and JDBC Stores

- Using a JDBC TLOG Store

- Using JMS Paging Stores

- Using Diagnostic Stores

Using the Default Persistent Store

Each server instance, including the administration server, has a default persistent store that requires no configuration. The default store is a file-based store that maintains its data in a group of files in a server instance's data\store\default directory. A directory for the default store is automatically created if one does not already exist. This default store is available to subsystems that do not require explicit selection of a particular store and function best by using the system's default storage mechanism. For example, a JMS Server with no persistent store configured will use the default store for its Managed Server and will support persistent messaging. See:

- Using the WebLogic Persistent Store in Configuring Server Environments for Oracle WebLogic Server.

- Modify the Default Store Settings in Oracle WebLogic Server Administration Console Help.

Using Custom File Stores and JDBC Stores

In addition to using the default file store, you can also configure a file store or JDBC store to suit your specific needs. A custom file store, like the default file store, maintains its data in a group of files in a directory. However, you may want to create a custom file store so that the file store's data is persisted to a particular storage device. When configuring a file store directory, the directory must be accessible to the server instance on which the file store is located.

A JDBC store can be configured when a relational database is used for storage. A JDBC store enables you to store persistent messages in a standard JDBC-capable database, which is accessed through a designated JDBC data source. The data is stored in the JDBC store's database table, which has a logical name of WLStore. It is up to the database administrator to configure the database for high availability and performance. See:

- When to Use a Custom Persistent Store in Configuring Server Environments for Oracle WebLogic Server.

- Comparing File Stores and JDBC Stores in Configuring Server Environments for Oracle WebLogic Server.

- Creating a Custom (User-Defined) File Store in Configuring Server Environments for Oracle WebLogic Server.

- Creating a JDBC Store in Configuring Server Environments for Oracle WebLogic Server.

Using a JDBC TLOG Store

You can configure a JDBC TLOG store to persist transaction logs to a database, which allows you to leverage replication and HA characteristics of the underlying database, simplify disaster recovery, and improve Transaction Recovery service migration. See "Using a JDBC TLog Store" in Configuring Server Environments for Oracle WebLogic Server.

Using JMS Paging Stores

Each JMS server implicitly creates a file based paging store. When the WebLogic Server JVM runs low on memory, this store is used to page non-persistent messages as well as persistent messages. Depending on the application, paging stores may generate heavy disk activity.

You can optionally change the directory location and the threshold settings at which paging begins. You can improve performance by locating paging store directories on a local file system, preferably in a temporary directory. Paging store files do not need to be backed up, replicated, or located in universally accessible location as they are automatically repopulated each time a JMS server restarts. See JMS Server Behavior in WebLogic Server 9.x and Later in Configuring and Managing JMS for Oracle WebLogic Server.

Note:

Paged persistent messages are potentially physical stored in two different places:

- Always in a recoverable default or custom store.

- Potentially in a paging directory.

Using Flash Storage to Page JMS Messages

You can often improve paging performance for JMS messages (persistent or non-persistent) by configuring JMS server paging directories to reference a directory on a locally mounted enterprise-class flash storage device. This can be significantly faster than other technologies

Note:

Most Flash storage devices are a single point of failure and are typically only accessible as a local device. They are suitable for JMS server paging stores which do not recover data after a failure and automatically reconstruct themselves as needed.

In most cases, Flash storage devices are not suitable for custom or default stores which typically contains data that must be safely recoverable. A configured Directory attribute of a default or custom store should not normally reference a directory that is on a single point of failure device.

Use the following steps to use a Flash storage device to page JMS messages:

1. Set the JMS server Message Paging Directory attribute to the path of your flash storage device, see Specifying a Message Paging Directory.

2. Tune the Message Buffer Size attribute (it controls when paging becomes active). You may be able to use lower threshold values as faster I/O operations provide improved load absorption. See Tuning the Message Buffer Size Option.

3. Tune JMS Server quotas to safely account for any Flash storage space limitations. This ensures that your JMS server(s) will not attempt to page more messages than the device can store, potentially yielding runtime errors and/or automatic shutdowns. As a conservative rule of thumb, assume page file usage will be at least 1.5 * ((Maximum Number of Active Messages) * (512 + average message body size)) rounded up to the nearest 16MB. See Defining Quota.

Using Diagnostic Stores

The Diagnostics store is a file store that implicitly always uses the Disabled synchronous write policy. It is dedicated to storing WebLogic server diagnostics information. One diagnostic store is configured per WebLogic Server instance. See "Configuring Diagnostic Archives" in Configuring and Using the Diagnostics Framework for Oracle WebLogic Server.

Best Practices When Using Persistent Stores

- For subsystems that share the same server instance, share one store between multiple subsystems rather than using a store per subsystem. Sharing a store is more efficient for the following reasons:

- A single store batches concurrent requests into single I/Os which reduces overall disk usage.

- Transactions in which only one resource participates are lightweight one-phase transactions. Conversely, transactions in which multiple stores participate become heavier weight two-phase transactions.

For example, configure all SAF agents and JMS servers that run on the same server instance so that they share the same store.

- Add a new store only when the old store(s) no longer scale.

Tuning JDBC Stores

The following section provides information on tuning JDBC Stores:

- Under heavy JDBC store I/O loads, you can improve performance by configuring a JDBC store to use multiple JDBC connections to concurrently process I/O operations. See "Enabling I/O Multithreading for JDBC Stores" in Configuring Server Environments for Oracle WebLogic Server.

- When using Oracle BLOBS, you may be able to improve performance by tuning the ThreeStepThreshold value. See "Enabling Oracle BLOB Record Columns" in Configuring Server Environments for Oracle WebLogic Server.

- The location of the JDBC store DDL that is used to initialize empty stores is now configurable. This simplifies the use of custom DDL for database table creation, which is sometimes used for database specific performance tuning. For information, see "Create JDBC stores" in Oracle WebLogic Server Administration Console Help and "Using the WebLogic Persistent Store" in Configuring Server Environments for Oracle WebLogic Server.

Tuning File Stores

The following section provides information on tuning File Stores:

- Basic Tuning Information

- Tuning a File Store Direct-Write-With-Cache Policy

- Tuning the File Store Direct-Write Policy

- Tuning the File Store Block Size

Basic Tuning Information

The following section provides general information on tuning File Stores:

- For basic (non-RAID) disk hardware, consider dedicating one disk per file store. A store can operate up to four to five times faster if it does not have to compete with any other store on the disk. Remember to consider the existence of the default file store in addition to each configured store and a JMS paging store for each JMS server.

- For custom and default file stores, tune the Synchronous Write Policy.

- There are three transactionally safe synchronous write policies: Direct-Write-With-Cache, Direct-Write, and Cache-Flush. Direct-Write-With-Cache is generally has the best performance of these policies, Cache-Flush generally has the lowest performance, and Direct-Write is the default. Unlike other policies, Direct-Write-With-Cache creates cache files in addition to primary files.

- The Disabled synchronous write policy is transactionally unsafe. The Disabled write-policy can dramatically improve performance, especially at low client loads. However, it is unsafe because writes become asynchronous and data can be lost in the event of Operating System or power failure.

- See Guidelines for Configuring a Synchronous Write Policy in Configuring Server Environments for Oracle WebLogic Server.

Note:

Certain older versions of Microsoft Windows may incorrectly report storage device synchronous write completion if the Windows default Write Cache Enabled setting is used. This violates the transactional semantics of transactional products (not specific to Oracle), including file stores configured with a Direct-Write (default) or Direct-Write-With-Cache policy, as a system crash or power failure can lead to a loss or a duplication of records/messages. One of the visible symptoms is that this problem may manifest itself in high persistent message/transaction throughput exceeding the physical capabilities of your storage device. You can address the problem by applying a Microsoft supplied patch, disabling the Windows Write Cache Enabled setting, or by using a power-protected storage device. See http://support.microsoft.com/kb/281672 and http://support.microsoft.com/kb/332023.

- When performing head-to-head vendor comparisons, make sure all the write policies for the persistent store are equivalent. Some non-WebLogic vendors default to the equivalent of Disabled.

- Depending on the synchronous write policy, custom and default stores have a variety of additional tunable attributes that may improve performance. These include CacheDirectory, MaxWindowBufferSize, IOBufferSize, BlockSize, InitialSize, and MaxFileSize. For more information see the JMSFileStoreMBean in the Oracle WebLogic Server MBean Reference.

Note:

.The JMSFileStoreMBean is deprecated, but the individual bean attributes apply to the non-deprecated beans for custom and default file stores.

- If disk performance continues to be a bottleneck, consider purchasing disk or RAID controller hardware that has a built-in write-back cache. These caches significantly improve performance by temporarily storing persistent data in volatile memory. To ensure transactionally safe write-back caches, they must be protected against power outages, host machine failure, and operating system failure. Typically, such protection is provided by a battery-backed write-back cache.

Tuning a File Store Direct-Write-With-Cache Policy

The Direct-Write-With-Cache synchronous write policy is commonly the highest performance option that still provides transactionally safe disk writes. It is typically not as high-performing as the Disabled synchronous write policy, but the Disabled policy is not a safe option for production systems unless you have some means to prevent loss of buffered writes during a system failure.

Direct-Write-With-Cache file stores write synchronously to a primary set of files in the location defined by the Directory attribute of the file store configuration. They also asynchronously write to a corresponding temporary cache file in the location defined by the CacheDirectory attribute of the file store configuration. The cache directory and the primary file serve different purposes and require different locations. In many cases, primary files should be stored in remote storage for high availability, whereas cache files are strictly for performance and not for high availability and can be stored locally.

When the Direct-Write-With-Cache synchronous write policy is selected, there are several additional tuning options that you should consider:

- Setting the CacheDirectory. For performance reasons, the cache directory should be located on a local file system. It is placed in the operating system temp directory by default.

- Increasing the MaxWindowBufferSize and IOBufferSize attributes. These tune native memory usage of the file store.

- Increasing the InitialSize and MaxFileSize tuning attributes. These tune the initial size of a store, and the maximum file size of a particular file in the store respectively.

- Tune the BlockSize attribute. See Tuning the File Store Block Size.

For more information on individual tuning parameters, see the JMSFileStoreMBean in the Oracle WebLogic Server MBean Reference.

Using Flash Storeage to Increase Performance

You can gain additional I/O performance by using enterprise-class flash drives, which can be significantly faster than spinning disks for accessing data in real-time applications and allows you to free up memory for other processing tasks.

Simply update the CacheDirectory attribute with the path to your flash storage device and ensure that the device contains sufficient free storage to accommodate a full copy of the store's primary files. See the CacheDirectory attribute in the Oracle WebLogic Server MBean Reference.

Additional Considerations

Consider the following when tuning the Direct-Write-With-Cache policy:

- There may be additional security and file locking considerations when using the Direct-Write-With-Cache synchronous write policy. See Securing a Production Environment for Oracle WebLogic Server and the CacheDirectory and LockingEnabled attributes of the JMSFileStoreMBean in the Oracle WebLogic Server MBean Reference.

- The JMSFileStoreMBean is deprecated, but the individual bean attributes apply to the non-deprecated beans for custom and default file stores.

- It is safe to delete a cache directory while the store is not running, but this may slow down the next store boot. Cache files are re-used to speed up the file store boot and recovery process, but only if the store's host WebLogic server has been shut down cleanly prior to the current boot (not after kill -9, nor after an OS/JVM crash) and there was no off-line change to the primary files (such as a store admin compaction). If the existing cache files cannot be safely used at boot time, they are automatically discarded and new files are created. In addition, a Warning log 280102 is generated. After a migration or failover event, this same Warning message is generated, but can be ignored.

- If the a Direct-Write-With-Cache file store fails to load a wlfileio native driver, the synchronous write policy automatically changes to the equivalent of Direct-Write with AvoidDirectIO=true. To view a running custom or default file store's configured and actual synchronous write policy and driver, examine the server log for WL-280008 and WL-280009 messages.

- To prevent unused cache files from consuming disk space, test and development environments may need to be modified to periodically delete cache files that are left over from temporarily created domains. In production environments, cache files are managed automatically by the file store.

Tuning the File Store Direct-Write Policy

Deprecation Note:

The AvoidDirectIO properties described in this section are still supported in this release, but have been deprecated as of 11gR1PS2. Use the configurable Direct-Write-With-Cache synchronous write policy as an alternative to the Direct-Write policy.

For file stores with the synchronous write policy of Direct-Write, you may be directed by Oracle Support or a release note to set weblogic.Server options on the command line or start script of the JVM that runs the store:

- Globally changes all stores running in the JVM:

-Dweblogic.store.AvoidDirectIO=true

- For a single store, where store-name is the name of the store:

-Dweblogic.store.store-name.AvoidDirectIO=true

- For the default store, where server-name is the name of the server hosting the store:

-Dweblogic.store._WLS_server-name.AvoidDirectIO=true

Setting AvoidDirectIO on an individual store overrides the setting of the global -Dweblogic.store.AvoidDirectIO option. For example: If you have two stores, A and B, and set the following options:

-Dweblogic.store.AvoidDirectIO=true
-Dweblogic.store.A.AvoidDirectIO=false

then only store B has the setting AvoidDirectIO=true.

Note:

Setting the AvoidDirectIO option may have performance implications which often can be mitigated using the block size setting described in Tuning the File Store Block Size.

Tuning the File Store Block Size

You may want to tune the file store block size for file stores that are configured with a synchronous write policy of Direct-Write (default), Direct-Write-With-Cache, or Cache-Flush, especially when using Direct-Write with AvoidDirectIO=true as described in Tuning the File Store Direct-Write Policy or for systems with a hard-drive-based write-back cache where you see that performance is limited by physical storage latency.

Consider the following example:

- A single WebLogic JMS producer sends persistent messages one by one.

- The network overhead is known to be negligible.

- The file store's disk drive has a 10,000 RPM rotational rate.

- The disk drive has a battery-backed write-back cache.

and the messaging rate is measured at 166 messages per second.

In this example, the low messaging rate matches the disk drive's latency (10,000 RPM / 60 seconds = 166 RPS) even though a much higher rate is expected due to the battery-backed write-back cache. Tuning the store's block size to match the file systems' block size could result in a significant improvement.

In some other cases, tuning the block size may result in marginal or no improvement:

- The caches are observed to yield low latency (so the I/O subsystem is not a significant bottleneck).

- Write-back caching is not used and performance is limited by larger disk drive latencies.

There may be a trade off between performance and file space when using higher block sizes. Multiple application records are packed into a single block only when they are written concurrently. Consequently, a large block size may cause a significant increase in store file sizes for applications that have little concurrent server activity and produce small records. In this case, one small record is stored per block and the remaining space in each block is unused. As an example, consider a Web Service Reliable Messaging (WS-RM) application with a single producer that sends small 100 byte length messages, where the application is the only active user of the store.

Oracle recommends tuning the store block size to match the block size of the file system that hosts the file store (typically 4096 for most file systems) when this yields a performance improvement. Alternately, tuning the block size to other values (such as paging and cache units) may yield performance gains. If tuning the block size does not yield a performance improvement, Oracle recommends leaving the block size at the default as this helps to minimize use of file system resources.

Setting the Block Size for a File Store

Deprecation Note:

The BlockSize command line properties that are described in this section are still supported in 11gR1PS2, but are deprecated. Oracle recommends using the BlockSize configurable on custom and default file stores instead.

To set the block size of a store, use one of the following properties on the command line or start script of the JVM that runs the store:

- Globally sets the block size of all file stores that don't have pre-existing files.

-Dweblogic.store.BlockSize=block-size

- Sets the block size for a specific file store that doesn't have pre-existing files.

-Dweblogic.store.store-name.BlockSize=block-size

- Sets the block size for the default file store, if the store doesn't have pre-existing files:

-Dweblogic.store._WLS_server-name. BlockSize=block-size

The value used to set the block size is an integer between 512 and 8192 which is automatically rounded down to the nearest power of 2.

Setting BlockSize on an individual store overrides the setting of the global -Dweblogic.store.BlockSize option. For example: If you have two stores, A and B, and set the following options:

-Dweblogic.store.BlockSize=8192
-Dweblogic.store.A.BlockSize=512

then store B has a block size of 8192 and store A has a block size of 512.

Note:

Setting the block size using command line properties only takes effect for file stores that have no pre-existing files. If a store has pre-existing files, the store continues to use the block size that was set when the store was first created.

Determining the File Store Block Size

You can verify a file store's current block size and synchronous write policy by viewing the server log of the server that hosts the store. Search for a "280009" store opened message.

Determining the File System Block Size

To determine your file system's actual block size, consult your operating system documentation. For example:

- Linux ext2 and ext3 file systems: run /sbin/dumpe2fs /dev/device-name and look for "Block size"

- Windows NTFS: run fsutil fsinfo ntfsinfo device letter: and look for "Bytes Per Cluster"

Converting a Store with Pre-existing Files

If the data in a store's pre-existing files do not need to be preserved, then simply shutdown the host WebLogic Server instance and delete the files to allow the block size to change when the store is restarted. If you need to preserve the data, convert a store with pre-existing files to a different block size by creating a version of the file store with the new block size using the compact command of the command line store administration utility:

1. java -Dweblogic.store.BlockSize=block-size weblogic.store.Admin

2. Type help for available commands.

3. Storeadmin->compact -dir file-store-directory

See "Store Administration Using a Java Command-line" in Configuring Server Environments for Oracle WebLogic Server.

Using a Network File System

The following sections provide information on using a WebLogic Perstistent Store with a Network File System (NFS):

- Configuring Synchronous Write Policies

- Test Server Restart Behavior

- Handling NFS Locking Errors

Configuring Synchronous Write Policies

NFS storage may not fully protect transactional data, as it may be configured to silently buffer synchronous write requests in volatile memory. If a file store Directory is located on an NFS mount, and the file store's Synchronous Write Policy is anything other than Disabled, check your NFS implementation and configuration to make sure that it is configured to support synchronous writes. A Disabled synchronous write policy does not perform synchronous writes, but, as a consequence, is generally not transactionally safe. You may detect undesirable buffering of synchronous write requests by observing high persistent message or transaction throughput that exceeds the physical capabilities of your storage device. On the NFS server, check the synchronous write setting of the exported NFS directory hosting your File Store. A SAN based file store, or a JDBC store, may provide an easier solution for safe centralized storage.

Test Server Restart Behavior

Oracle strongly recommends verifying the behavior of a server restart after abrupt machine failures when the JMS messages and transaction logs are stored on an NFS mounted directory. Depending on the NFS implementation, different issues can arise after a failover or restart. The behavior can be verified by abruptly shutting down the node hosting the Web Logic servers while these are running. If the server is configured for server migration, it should be started automatically in the failover node after the corresponding failover period. If not, a manual restart of the WebLogic Server on the same host (after the node has completely rebooted) can be performed.

Handling NFS Locking Errors

Note:

You can configure a NFS v4 based Network Attached Storage (NAS) server to release locks within the approximate time required to complete server migration. If you tune and test your NFS v4 environment, you do not need to follow the procedures in this section. See your storage vendor's documentation for information on locking files stored in NFS-mounted directories on the storage device.

If Oracle WebLogic Server does not restart after abrupt machine failure when JMS messages and transaction logs are stored on NFS mounted directory, the following errors may appear in the server log files:

Example 8-1 Store Restart Failure Error Message

MMM dd, yyyy hh:mm:ss a z> <Error> <Store> <BEA-280061> <The persistent store "_WLS_server_soa1" could not be deployed:
weblogic.store.PersistentStoreException: java.io.IOException:
[Store:280021]There was an error while opening the file store file "_WLS_SERVER_SOA1000000.DAT"
at weblogic.store.io.file.Heap.open(Heap.java:168)
at weblogic.store.io.file.FileStoreIO.open(FileStoreIO.java:88)
...
java.io.IOException: Error from fcntl() for file locking, Resource temporarily unavailable, errno=11

This error is due to the NFS system not releasing the lock on the stores. WebLogic Server maintains locks on files used for storing JMS data and transaction logs to protect from potential data corruption if two instances of the same WebLogic Server are accidentally started. The NFS storage device does not become aware of machine failure in a timely manner and the locks are not released by the storage device. As a result, after abrupt machine failure, followed by a restart, any subsequent attempt by WebLogic Server to acquire locks on the previously locked files may fail. Refer to your storage vendor documentation for additional information on the locking of files stored in NFS mounted directories on the storage device. If it is not reasonably possible to tune locking behavior in your NFS environment, use one of the following two solutions to unlock the logs and data files.

Use one of the following two solutions to unlock the logs and data files:

- Solution 1 - Copying Data Files to Remove NFS Locks

- Solution 2 - Disabling File Locks in WebLogic Server File Stores

Solution 1 - Copying Data Files to Remove NFS Locks

Manually unlock the logs and JMS data files and start the servers by creating a copy of the locked persistence store file and using the copy for subsequent operations. To create a copy of the locked persistence store file, rename the file, and then copy it back to its original name. The following sample steps assume that transaction logs are stored in the /shared/tlogs directory and JMS data is stored in the /shared/jms directory.

Example 8-2 Sample Steps to Remove NFS Locks

cd /shared/tlogs
mv _WLS_SOA_SERVER1000000.DAT _WLS_SOA_SERVER1000000.DAT.old
cp _WLS_SOA_SERVER1000000.DAT.old _WLS_SOA_SERVER1000000.DAT
cd /shared/jms
mv SOAJMSFILESTORE_AUTO_1000000.DAT SOAJMSFILESTORE_AUTO_1000000.DAT.old
cp SOAJMSFILESTORE_AUTO_1000000.DAT.old SOAJMSFILESTORE_AUTO_1000000.DAT
mv UMSJMSFILESTORE_AUTO_1000000.DAT UMSJMSFILESTORE_AUTO_1000000.DAT.old
cp UMSJMSFILESTORE_AUTO_1000000.DAT.old UMSJMSFILESTORE_AUTO_1000000.DAT

With this solution, the WebLogic file locking mechanism continues to provide protection from any accidental data corruption if multiple instances of the same servers were accidently started. However, the servers must be restarted manually after abrupt machine failures. File stores will create multiple consecutively numbered.DAT files when they are used to store large amounts of data. All files may need to be copied and renamed when this occurs.

Solution 2 - Disabling File Locks in WebLogic Server File Stores

Note:

With this solution, since the WebLogic Server locking is disabled, automated server restarts and failovers should succeed. Be very cautious, however, when using this option. The WebLogic file locking feature is designed to help prevent severe file corruptions that can occur in undesired concurrency scenarios. If the server using the file store is configured for server migration, always configure the database based leasing option. This enforces additional locking mechanisms using database tables, and prevents automated restart of more than one instance of the same WebLogic Server. Additional procedural precautions must be implemented to avoid any human error and to ensure that one and only one instance of a server is manually started at any give point in time. Similarly, extra precautions must be taken to ensure that no two domains have a store with the same name that references the same directory.

You can also use the WebLogic Server Administration Console to disable WebLogic file locking mechanisms for the default file store, a custom file store, a JMS paging file store, and a Diagnostics file store, as described in the following sections:

- Disabling File Locking for the Default File Store

- Disabling File Locking for a Custom File Store

- Disabling File Locking for a JMS Paging File Store

- Disabling File Locking for a Diagnostics File Store

Disabling File Locking for the Default File Store

Follow these steps to disable file locking for the default file store using the WebLogic Server Administration Console:

1. If necessary, click Lock & Edit in the Change Center (upper left corner) of the Administration Console to get an Edit lock for the domain.

2. 2. In the Domain Structure tree, expand the Environment node and select Servers.

3. In the Summary of Servers list, select the server you want to modify.

4. Select the Configuration > Services tab.

5. Scroll down to the Default Store section and click Advanced.

6. Scroll down and deselect the Enable File Locking check box.

7. Click Save to save the changes. If necessary, click Activate Changes in the Change Center.

8. Restart the server you modified for the changes to take effect.

The resulting config.xml entry looks like:

Example 8-3 Example config.xml Entry for Disabling File Locking for a Default File Store

<server>
<name>examplesServer</name>
...
<default-file-store>
<synchronous-write-policy>Direct-Write</synchronous-write-policy>
<io-buffer-size>-1</io-buffer-size>
<max-file-size>1342177280</max-file-size>
<block-size>-1</block-size>
<initial-size>0</initial-size>
<file-locking-enabled>false</file-locking-enabled>
</default-file-store>
</server>

Disabling File Locking for a Custom File Store

Use the following steps to disable file locking for a custom file store using the WebLogic Server Administration Console:

1. If necessary, click Lock & Edit in the Change Center (upper left corner) of the Administration Console to get an Edit lock for the domain.

2. In the Domain Structure tree, expand the Services node and select Persistent Stores.

3. In the Summary of Persistent Stores list, select the custom file store you want to modify.

4. On the Configuration tab for the custom file store, click Advanced to display advanced store settings.

5. Scroll down to the bottom of the page and deselect the Enable File Locking check box.

6. Click Save to save the changes. If necessary, click Activate Changes in the Change Center.

7. If the custom file store was in use, you must restart the server for the changes to take effect.

The resulting config.xml entry looks like:

Example 8-4 Example config.xml Entry for Disabling File Locking for a Custom File Store

<file-store>
<name>CustomFileStore-0</name>
<directory>C:\custom-file-store</directory>
<synchronous-write-policy>Direct-Write</synchronous-write-policy>
<io-buffer-size>-1</io-buffer-size>
<max-file-size>1342177280</max-file-size>
<block-size>-1</block-size>
<initial-size>0</initial-size>
<file-locking-enabled>false</file-locking-enabled>
<target>examplesServer</target>
</file-store>

Disabling File Locking for a JMS Paging File Store

Use the following steps to disable file locking for a JMS paging file store using the WebLogic Server Administration Console:

1. If necessary, click Lock & Edit in the Change Center (upper left corner) of the Administration Console to get an Edit lock for the domain.

2. In the Domain Structure tree, expand the Services node, expand the Messaging node, and select JMS Servers.

3. In the Summary of JMS Servers list, select the JMS server you want to modify.

4. On the Configuration > General tab for the JMS Server, scroll down and deselect the Paging File Locking Enabled check box.

5. Click Save to save the changes. If necessary, click Activate Changes in the Change Center.

6. Restart the server you modified for the changes to take effect.

The resulting config.xml entry looks like:

Example 8-5 Example config.xml Entry for Disabling File Locking for a JMS Paging File Store

<jms-server>
<name>examplesJMSServer</name>
<target>examplesServer</target>
<persistent-store>exampleJDBCStore</persistent-store>
...
<paging-file-locking-enabled>false</paging-file-locking-enabled>
...
</jms-server>

Disabling File Locking for a Diagnostics File Store

Use the following steps to disable file locking for a Diagnostics file store using the WebLogic Server Administration Console:

1. If necessary, click Lock & Edit in the Change Center (upper left corner) of the Administration Console to get an Edit lock for the domain.

2. In the Domain Structure tree, expand the Diagnostics node and select Archives.

3. In the Summary of Diagnostic Archives list, select the server name of the archive that you want to modify.

4. On the Settings for [server_name] page, deselect the Diagnostic Store File Locking Enabled check box.

5. Click Save to save the changes. If necessary, click Activate Changes in the Change Center.

6. Restart the server you modified for the changes to take effect.

The resulting config.xml entry looks like:

Example 8-6 Example config.xml Entry for Disabling File Locking for a Diagnostics File Store

<server>
<name>examplesServer</name>
...
<server-diagnostic-config>
<diagnostic-store-dir>data/store/diagnostics</diagnostic-store-dir>
<diagnostic-store-file-locking-enabled>false</diagnostic-store-file-lockingenabled>
<diagnostic-data-archive-type>FileStoreArchive</diagnostic-data-archive-type>
<data-retirement-enabled>true</data-retirement-enabled>
<preferred-store-size-limit>100</preferred-store-size-limit>
<store-size-check-period>1</store-size-check-period>
</server-diagnostic-config>
</server>

9 DataBase Tuning

This chapter describes how to tune your database to prevent it from becoming a major enterprise-level bottleneck. Configure your database for optimal performance by following the tuning guidelines in this chapter and in the product documentation for the database you are using.

- General Suggestions

- Database-Specific Tuning

General Suggestions

This section provides general database tuning suggestions:

- Good database design — Distribute the database workload across multiple disks to avoid or reduce disk overloading. Good design also includes proper sizing and organization of tables, indexes, and logs.

- Disk I/O optimization — Disk I/O optimization is related directly to throughput and scalability. Access to even the fastest disk is orders of magnitude slower than memory access. Whenever possible, optimize the number of disk accesses. In general, selecting a larger block/buffer size for I/O reduces the number of disk accesses and might substantially increase throughput in a heavily loaded production environment.

- Checkpointing — This mechanism periodically flushes all dirty cache data to disk, which increases the I/O activity and system resource usage for the duration of the checkpoint. Although frequent checkpointing can increase the consistency of on-disk data, it can also slow database performance. Most database systems have checkpointing capability, but not all database systems provide user-level controls. Oracle, for example, allows administrators to set the frequency of checkpoints while users have no control over SQLServer 7.x checkpoints. For recommended settings, see the product documentation for the database you are using.

- Disk and database overhead can sometimes be dramatically reduced by batching multiple operations together and/or increasing the number of operations that run in parallel (increasing concurrency). Examples:

- Increasing the value of the Message bridge BatchSize or the Store-and-Forward WindowSize can improve performance as larger batch sizes produce fewer but larger I/Os.

- Programmatically leveraging JDBC's batch APIs.

- Use the MDB transaction batching feature. See Chapter 11, "Tuning Message-Driven Beans".

- Increasing concurrency by increasing max-beans-in-free-pool and thread pool size for MDBs (or decreasing it if batching can be leveraged).

Database-Specific Tuning

The following sections provide basic tuning suggestions for Oracle, SQL Server, and Sybase:

- Oracle

- Microsoft SQL Server

- Sybase

Note:

Always check the tuning guidelines in your database-specific vendor documentation.

Oracle

This section describes performance tuning for Oracle.

- Number of processes — On most operating systems, each connection to the Oracle server spawns a shadow process to service the connection. Thus, the maximum number of processes allowed for the Oracle server must account for the number of simultaneous users, as well as the number of background processes used by the Oracle server. The default number is usually not big enough for a system that needs to support a large number of concurrent operations. For platform-specific issues, see your Oracle administrator's guide. The current setting of this parameter can be obtained with the following query:

SELECT name, value FROM v$parameter WHERE name = 'processes';

- Buffer pool size —The buffer pool usually is the largest part of the Oracle server system global area (SGA). This is the location where the Oracle server caches data that it has read from disk. For read-mostly applications, the single most important statistic that affects data base performance is the buffer cache hit ratio. The buffer pool should be large enough to provide upwards of a 95% cache hit ratio. Set the buffer pool size by changing the value, in data base blocks, of the db_cache_size parameter in the init.ora file.

- Shared pool size — The share pool in an important part of the Oracle server system global area (SGA). The SGA is a group of shared memory structures that contain data and control information for one Oracle database instance. If multiple users are concurrently connected to the same instance, the data in the instance's SGA is shared among the users. The shared pool portion of the SGA caches data for two major areas: the library cache and the dictionary cache. The library cache stores SQL-related information and control structures (for example, parsed SQL statement, locks). The dictionary cache stores operational metadata for SQL processing.
For most applications, the shared pool size is critical to Oracle performance. If the shared pool is too small, the server must dedicate resources to managing the limited amount of available space. This consumes CPU resources and causes contention because Oracle imposes restrictions on the parallel management of the various caches. The more you use triggers and stored procedures, the larger the shared pool must be. The SHARED_POOL_SIZE initialization parameter specifies the size of the shared pool in bytes.

The following query monitors the amount of free memory in the share pool:

SELECT * FROM v$sgastat
WHERE name = 'free memory' AND pool = 'shared pool';

- Maximum opened cursor — To prevent any single connection taking all the resources in the Oracle server, the OPEN_CURSORS initialization parameter allows administrators to limit the maximum number of opened cursors for each connection. Unfortunately, the default value for this parameter is too small for systems such as WebLogic Server. Cursor information can be monitored using the following query:

SELECT name, value FROM v$sysstat
WHERE name LIKE 'opened cursor%';

- Database block size — A block is Oracle's basic unit for storing data and the smallest unit of I/O. One data block corresponds to a specific number of bytes of physical database space on disk. This concept of a block is specific to Oracle RDBMS and should not be confused with the block size of the underlying operating system. Since the block size affects physical storage, this value can be set only during the creation of the database; it cannot be changed once the database has been created. The current setting of this parameter can be obtained with the following query:

SELECT name, value FROM v$parameter WHERE name = 'db_block_size';

- Sort area size — Increasing the sort area increases the performance of large sorts because it allows the sort to be performed in memory during query processing. This can be important, as there is only one sort area for each connection at any point in time. The default value of this init.ora parameter is usually the size of 6–8 data blocks. This value is usually sufficient for OLTP operations but should be increased for decision support operation, large bulk operations, or large index-related operations (for example, recreating an index). When performing these types of operations, you should tune the following init.ora parameters (which are currently set for 8K data blocks):

sort_area_size = 65536
sort_area_retained_size = 65536

Microsoft SQL Server

The following guidelines pertain to performance tuning parameters for Microsoft SQL Server databases. For more information about these parameters, see your Microsoft SQL Server documentation.

- Store tempdb on a fast I/O device.

- Increase the recovery interval if perfmon shows an increase in I/O.

- Use an I/O block size larger than 2 KB.

Sybase

The following guidelines pertain to performance tuning parameters for Sybase databases. For more information about these parameters, see your Sybase documentation.

- Lower recovery interval setting results in more frequent checkpoint operations, resulting in more I/O operations.

- Use an I/O block size larger than 2 KB.

- Sybase controls the number of engines in a symmetric multiprocessor (SMP) environment. They recommend configuring this setting to equal the number of CPUs minus 1.

10 Tuning WebLogic Server EJBs

This chapter describe how to tune WebLogic Server EJBs for your application environment.

- General EJB Tuning Tips

- Tuning EJB Caches

- Tuning EJB Pools

- CMP Entity Bean Tuning

- Tuning In Response to Monitoring Statistics

- Using the JDT Compiler

General EJB Tuning Tips

- Deployment descriptors are schema-based. Descriptors that are new in this release of WebLogic Server are not available as DTD-based descriptors.

- Avoid using the RequiresNew transaction parameter. Using RequiresNew causes the EJB container to start a new transaction after suspending any current transactions. This means additional resources, including a separate data base connection are allocated.

- Use local-interfaces or set call-by-reference to true to avoid the overhead of serialization when one EJB calls another or an EJB is called by a servlet/JSP in the same application. Note the following:

- In release prior to WebLogic Server 8.1, call-by-reference is turned on by default. For releases of WebLogic Server 8.1 and higher, call-by-reference is turned off by default. Older applications migrating to WebLogic Server 8.1 and higher that do not explicitly turn on call-by-reference may experience a drop in performance.

- This optimization does not apply to calls across different applications.

- Use Stateless session beans over Stateful session beans whenever possible. Stateless session beans scale better than stateful session beans because there is no state information to be maintained.

- WebLogic Server provides additional transaction performance benefits for EJBs that reside in a WebLogic Server cluster. When a single transaction uses multiple EJBs, WebLogic Server attempts to use EJB instances from a single WebLogic Server instance, rather than using EJBs from different servers. This approach minimizes network traffic for the transaction. In some cases, a transaction can use EJBs that reside on multiple WebLogic Server instances in a cluster. This can occur in heterogeneous clusters, where all EJBs have not been deployed to all WebLogic Server instances. In these cases, WebLogic Server uses a multitier connection to access the datastore, rather than multiple direct connections. This approach uses fewer resources, and yields better performance for the transaction. However, for best performance, the cluster should be homogeneous — all EJBs should reside on all available WebLogic Server instances.

Tuning EJB Caches

The following sections provide information on how to tune EJB caches:

- Tuning the Stateful Session Bean Cache

- Tuning the Entity Bean Cache

- Tuning the Query Cache

Tuning the Stateful Session Bean Cache

The EJB Container caches stateful session beans in memory up to a count specified by the max-beans-in-cache parameter specified in weblogic-ejb-jar.xml. This parameter should be set equal to the number of concurrent users. This ensures minimum passivation of stateful session beans to disk and subsequent activation from disk which yields better performance.

Tuning the Entity Bean Cache

Entity beans are cached at two levels by the EJB container:

- Transaction-Level Caching

- Caching between Transactions

- Ready Bean Caching

Transaction-Level Caching

Once an entity bean has been loaded from the database, it is always retrieved from the cache whenever it is requested when using the findByPrimaryKey or invoked from a cached reference in that transaction. Getting an entity bean using a non-primary key finder always retrieves the persistent state of the bean from the data base.

Caching between Transactions

Entity bean instances are also cached between transactions. However, by default, the persistent state of the entity beans are not cached between transactions. To enable caching between transactions, set the value of the cache-between-transactions parameter to true.

Is it safe to cache the state? This depends on the concurrency-strategy for that bean. The entity-bean cache is really only useful when cache-between-transactions can be safely set to true. In cases where ejbActivate() and ejbPassivate() callbacks are expensive, it is still a good idea to ensure the entity-cache size is large enough. Even though the persistent state may be reloaded at least once per transaction, the beans in the cache are already activated. The value of the cache-size is set by the deployment descriptor parameter max-beans-in-cache and should be set to maximize cache-hits. In most situations, the value need not be larger than the product of the number of rows in the table associated with the entity bean and the number of threads expected to access the bean concurrently.

Ready Bean Caching

For entity beans with a high cache miss ratio, maintaining ready bean instances can adversely affect performance.

If you can set disable-ready-instances in the entity-cache element of an entity-descriptor, the container does not maintain the ready instances in cache. If the feature is enabled in the deployment descriptor, the cache only keeps the active instances. Once the involved transaction is committed or rolled back, the bean instance is moved from active cache to the pool immediately.

Tuning the Query Cache

Query Caching is a new feature in WebLogic Server 9.0 that allows read-only CMP entity beans to cache the results of arbitrary finders. Query caching is supported for all finders except prepared-query finders. The query cache can be an application-level cache as well as a bean-level cache. The size of the cache is limited by the weblogic-ejb-jar.xml parameter max-queries-in-cache. The finder-level flag in the weblogic-cmp-rdbms descriptor file, enable-query-caching is used to specify whether the results of that finder are to be cached. A flag with the same name has the same purpose for internal relationship finders when applied to the weblogic-relationship-role element. Queries are evicted from the query-cache under the following circumstances:

- The query is least recently used and the query-cache has hit its size limit.

- At least one of the EJBs that satisfy the query has been evicted from the entity bean cache, regardless of the reason.

- The query corresponds to a finder that has eager-relationship-caching enabled and the query for the associated internal relationship finder has been evicted from the related bean's query cache.

It is possible to let the size of the entity-bean cache limit the size of the query-cache by setting the max-queries-in-cache parameter to 0, since queries are evicted from the cache when the corresponding EJB is evicted. This may avoid some lock contention in the query cache, but the performance gain may not be significant.

Tuning EJB Pools

The following section provides information on how to tune EJB pools:

- Tuning the Stateless Session Bean Pool

- Tuning the MDB Pool

- Tuning the Entity Bean Pool

Tuning the Stateless Session Bean Pool

The EJB container maintains a pool of stateless session beans to avoid creating and destroying instances. Though generally useful, this pooling is even more important for performance when the ejbCreate() and the setSessionContext() methods are expensive. The pool has a lower as well as an upper bound. The upper bound is the more important of the two.

- The upper bound is specified by the max-beans-in-free-pool parameter. It should be set equal to the number of threads expected to invoke the EJB concurrently. Using too small of a value impacts concurrency.

- The lower bound is specified by the initial-beans-in-free-pool parameter. Increasing the value of initial-beans-in-free-pool increases the time it takes to deploy the application containing the EJB and contributes to startup time for the server. The advantage is the cost of creating EJB instances is not incurred at run time. Setting this value too high wastes memory.

Tuning the MDB Pool

The life cycle of MDBs is very similar to stateless session beans. The MDB pool has the same tuning parameters as stateless session beans and the same factors apply when tuning them. In general, most users will find that the default values are adequate for most applications. See Chapter 11, "Tuning Message-Driven Beans".

Tuning the Entity Bean Pool

The entity bean pool serves two purposes:

- A target objects for invocation of finders via reflection.

- A pool of bean instances the container can recruit if it cannot find an instance for a particular primary key in the cache.

The entity pool contains anonymous instances (instances that do not have a primary key). These beans are not yet active (meaning ejbActivate() has not been invoked on them yet), though the EJB context has been set. Entity bean instances evicted from the entity cache are passivated and put into the pool. The tunables are the initial-beans-in-free-pool and max-beans-in-free-pool. Unlike stateless session beans and MDBs, the max-beans-in-free-pool has no relation with the thread count. You should increase the value of max-beans-in-free-pool if the entity bean constructor or setEnityContext() methods are expensive.

CMP Entity Bean Tuning

The largest performance gains in entity beans are achieved by using caching to minimize the number of interactions with the data base. However, in most situations, it is not realistic to be able to cache entity beans beyond the scope of a transaction. The following sections provide information on WebLogic Server EJB container features, most of which are configurable, that you can use to minimize database interaction safely:

- Use Eager Relationship Caching

- Use JDBC Batch Operations

- Tuned Updates

- Using Field Groups

- include-updates

- call-by-reference

- Bean-level Pessimistic Locking

- Concurrency Strategy

Use Eager Relationship Caching

Using eager relationship caching allows the EJB container to load related entity beans using a single SQL join. Use only when the same transaction accesses related beans. See "Relationship Caching" in Programming WebLogic Enterprise JavaBeans for Oracle WebLogic Server.

In this release of WebLogic Server, if a CMR field has specified both relationship-caching and cascade-delete, the owner bean and related bean are loaded to SQL which can provide an additional performance benefit.

Using Inner Joins

The EJB container always uses an outer join in a CMP bean finder when eager relationship-caching is turned on. Typically, inner joins are faster to execute than outer joins with the drawback that inner joins do not return rows which do not have data in the corresponding joined table. Where applicable, using an inner join on very large databases may help to free CPU resources.

In WLS 10.3, use-inner-join has been added in weblogic-cmp-rdbms-jar.xml, as an attribute of the weblogic-rdbms-bean, as shown here:

<weblogic-rdbms-bean>

<ejb-name>exampleBean</ejb-name>

...

<use-inner-join>true</use-inner-join>

</weblogic-rdbms-bean>

This element should only be set to true if the CMP bean's related beans can never be null or an empty set.

The default value is false. If you specify its value as true, all relationship cache query on the entity bean use an inner join instead of a left outer join to execute a select query clause.

Use JDBC Batch Operations

JDBC batch operations are turned on by default in the EJB container. The EJB container automatically re-orders and executes similar data base operations in a single batch which increases performance by eliminating the number of data base round trips. Oracle recommends using batch operations.

Tuned Updates

When an entity EJB is updated, the EJB container automatically updates in the data base only those fields that have actually changed. As a result the update statements are simpler and if a bean has not been modified, no data base call is made. Because different transactions may modify different sets of fields, more than one form of update statements may be used to store the bean in the data base. It is important that you account for the types of update statements that may be used when setting the size of the prepared statement cache in the JDBC connection pool. See Cache Prepared and Callable Statements.

Using Field Groups

Field groups allow the user to segregate commonly used fields into a single group. If any of the fields in the group is accessed by application/bean code, the entire group is loaded using a single SQL statement. This group can also be associated with a finder. When the finder is invoked and finders-load-bean is true, it loads only those fields from the data base that are included in the field group. This means that if most transactions do not use a particular field that is slow to load, such as a BLOB, it can be excluded from a field-group. Similarly, if an entity bean has a lot of fields, but a transaction uses only a small number of them, the unused fields can be excluded.

Note:

Be careful to ensure that fields that are accessed in the same transaction are not configured into separate field-groups. If that happens, multiple data base calls occur to load the same bean, when one would have been enough.

include-updates

This flag causes the EJB container to flush all modified entity beans to the data base before executing a finder. If the application modifies the same entity bean more than once and executes a non-pk finder in-between in the same transaction, multiple updates to the data base are issued. This flag is turned on by default to comply with the EJB specification.

If the application has transactions where two invocations of the same or different finders could return the same bean instance and that bean instance could have been modified between the finder invocations, it makes sense leaving include-updates turned on. If not, this flag may be safely turned off. This eliminates an unnecessary flush to the data base if the bean is modified again after executing the second finder. This flag is specified for each finder in the cmp-rdbms descriptor.

call-by-reference

When it is turned off, method parameters to an EJB are passed by value, which involves serialization. For mutable, complex types, this can be significantly expensive. Consider using for better performance when:

- The application does not require call-by-value semantics, such as method parameters are not modified by the EJB.

or

- If modified by the EJB, the changes need not be invisible to the caller of the method.

This flag applies to all EJBs, not just entity EJBs. It also applies to EJB invocations between servlets/JSPs and EJBs in the same application. The flag is turned off by default to comply with the EJB specification. This flag is specified at the bean-level in the WebLogic-specific deployment descriptor.

Bean-level Pessimistic Locking

Bean-level pessimistic locking is implemented in the EJB container by acquiring a data base lock when loading the bean. When implemented, each entity bean can only be accessed by a single transaction in a single server at a time. All other transactions are blocked, waiting for the owning transaction to complete. This is a useful alternative to using a higher data base isolation level, which can be expensive at the RDBMS level. This flag is specified at the bean level in the cmp-rdbms deployment descriptor.

Note:

If the lock is not exclusive lock, you man encounter deadlock conditions. If the data base lock is a shared lock, there is potential for deadlocks when using that RDBMS.

Concurrency Strategy

The concurrency-strategy deployment descriptor tells the EJB container how to handle concurrent access of the same entity bean by multiple threads in the same server instance. Set this parameter to one of four values:

- Exclusive—The EJB container ensures there is only one instance of an EJB for a given primary key and this instance is shared among all concurrent transactions in the server with the container serializing access to it. This concurrency setting generally does not provide good performance unless the EJB is used infrequently and chances of concurrent access is small.

- Database—This is the default value and most commonly used concurrency strategy. The EJB container defers concurrency control to the database. The container maintains multiple instances of an EJB for a given primary-key and each transaction gets it's own copy. In combination with this strategy, the database isolation-level and bean level pessimistic locking play a major role in determining if concurrent access to the persistent state should be allowed. It is possible for multiple transactions to access the bean concurrently so long as it does not need to go to the database, as would happen when the value of cache-between-transactions is true. However, setting the value of cache-between-transactions to true unsafe and not recommended with the Dababase concurrency strategy.

- Optimistic—The goal of the optimistic concurrency strategy is to minimize locking at the data base and while continuing to provide data consistency. The basic assumption is that the persistent state of the EJB is changed very rarely. The container attempts to load the bean in a nested transaction so that the isolation-level settings of the outer transaction does not cause locks to be acquired at the data base. At commit-time, if the bean has been modified, a predicated update is used to ensure it's persistent state has not been changed by some other transaction. If so, an OptimisticConcurrencyException is thrown and must be handled by the application.
Since EJBs that can use this concurrency strategy are rarely modified, using cache-between-transactions on can boost performance significantly. This strategy also allows commit-time verification of beans that have been read, but not changed. This is done by setting the verify-rows parameter to Read in the cmp-rdbms descriptor. This provides very high data-consistency while at the same time minimizing locks at the data base. However, it does slow performance somewhat. It is recommended that the optimistic verification be performed using a version column: it is faster, followed closely by timestamp, and more distantly by modified and read. The modified value does not apply if verify-rows is set to Read.

When an optimistic concurrency bean is modified in a server that is part of a cluster, the server attempts to invalidate all instances of that bean cluster-wide in the expectation that it will prevent OptimisticConcurrencyExceptions. In some cases, it may be more cost effective to simply let other servers throw an OptimisticConcurrencyException. in this case, turn off the cluster-wide invalidation by setting the cluster-invalidation-disabled flag in the cmp-rdbms descriptor.

- ReadOnly—The ReadOnly value is the most performant. When selected, the container assumes the EJB is non-transactional and automatically turns on cache-between-transactions. Bean states are updated from the data base at periodic, configurable intervals or when the bean has been programmatically invalidated. The interval between updates can cause the persistent state of the bean to become stale. This is the only concurrency-strategy for which query-caching can be used. See Caching between Transactions.

Tuning In Response to Monitoring Statistics

The WebLogic Server Administration Console reports a wide variety of EJB runtime monitoring statistics, many of which are useful for tuning your EJBs. This section discusses how some of these statistics can help you tune the performance of EJBs.

To display the statistics in the Administration Console, see "Monitoring EJBs" in Oracle WebLogic Server Administration Console Help. If you prefer to write a custom monitoring application, you can access the monitoring statistics using JMX or WLST by accessing the relevant runtime MBeans. See "Runtime MBeans" in Oracle WebLogic Server MBean Reference.

Cache Miss Ratio

The cache miss ratio is a ratio of the number of times a container cannot find a bean in the cache (cache miss) to the number of times it attempts to find a bean in the cache (cache access):

Cache Miss Ratio = (Cache Total Miss Count / Cache Total Access Count) * 100

A high cache miss ratio could be indicative of an improperly sized cache. If your application uses a certain subset of beans (read primary keys) more frequently than others, it would be ideal to size your cache large enough so that the commonly used beans can remain in the cache as less commonly used beans are cycled in and out upon demand. If this is the nature of your application, you may be able to decrease your cache miss ratio significantly by increasing the maximum size of your cache.

If your application doesn't necessarily use a subset of beans more frequently than others, increasing your maximum cache size may not affect your cache miss ratio. We recommend testing your application with different maximum cache sizes to determine which give the lowest cache miss ratio. It is also important to keep in mind that your server has a finite amount of memory and therefore there is always a trade-off to increasing your cache size.

Lock Waiter Ratio

When using the Exclusive concurrency strategy, the lock waiter ratio is the ratio of the number of times a thread had to wait to obtain a lock on a bean to the total amount of lock requests issued:

Lock Waiter Ratio = (Current Waiter Count / Current Lock Entry Count) * 100

A high lock waiter ratio can indicate a suboptimal concurrency strategy for the bean. If acceptable for your application, a concurrency strategy of Database or Optimistic will allow for more parallelism than an Exclusive strategy and remove the need for locking at the EJB container level.

Because locks are generally held for the duration of a transaction, reducing the duration of your transactions will free up beans more quickly and may help reduce your lock waiter ratio. To reduce transaction duration, avoid grouping large amounts of work into a single transaction unless absolutely necessary.

Lock Timeout Ratio

When using the Exclusive concurrency strategy, the lock timeout ratio is the ratio of timeouts to accesses for the lock manager:

Lock Timeout Ratio =(Lock Manager Timeout Total Count / Lock Manager Total Access Count) * 100

The lock timeout ratio is closely related to the lock waiter ratio. If you are concerned about the lock timeout ratio for your bean, first take a look at the lock waiter ratio and our recommendations for reducing it (including possibly changing your concurrency strategy). If you can reduce or eliminate the number of times a thread has to wait for a lock on a bean, you will also reduce or eliminate the amount of timeouts that occur while waiting.

A high lock timeout ratio may also be indicative of an improper transaction timeout value. The maximum amount of time a thread will wait for a lock is equal to the current transaction timeout value.

If the transaction timeout value is set too low, threads may not be waiting long enough to obtain access to a bean and timing out prematurely. If this is the case, increasing the trans-timeout-seconds value for the bean may help reduce the lock timeout ratio.

Take care when increasing the trans-timeout-seconds, however, because doing so can cause threads to wait longer for a bean and threads are a valuable server resource. Also, doing so may increase the request time, as a request ma wait longer before timing out.

Pool Miss Ratio

The pool miss ratio is a ratio of the number of times a request was made to get a bean from the pool when no beans were available, to the total number of requests for a bean made to the pool:

Pool Miss Ratio = (Pool Total Miss Count / Pool Total Access Count) * 100

If your pool miss ratio is high, you must determine what is happening to your bean instances. There are three things that can happen to your beans.

- They are in use.

- They were destroyed.

- They were removed.

Follow these steps to diagnose the problem:

1. Check your destroyed bean ratio to verify that bean instances are not being destroyed.

2. Investigate the cause and try to remedy the situation.

3. Examine the demand for the EJB, perhaps over a period of time.

One way to check this is via the Beans in Use Current Count and Idle Beans Count displayed in the Administration Console. If demand for your EJB spikes during a certain period of time, you may see a lot of pool misses as your pool is emptied and unable to fill additional requests.

As the demand for the EJB drops and beans are returned to the pool, many of the beans created to satisfy requests may be unable to fit in the pool and are therefore removed. If this is the case, you may be able to reduce the number of pool misses by increasing the maximum size of your free pool. This may allow beans that were created to satisfy demand during peak periods to remain in the pool so they can be used again when demand once again increases.

Destroyed Bean Ratio

The destroyed bean ratio is a ratio of the number of beans destroyed to the total number of requests for a bean.

Destroyed Bean Ratio = (Total Destroyed Count / Total Access Count) * 100

To reduce the number of destroyed beans, Oracle recommends against throwing non-application exceptions from your bean code except in cases where you want the bean instance to be destroyed. A non-application exception is an exception that is either a java.rmi.RemoteException (including exceptions that inherit from RemoteException) or is not defined in the throws clause of a method of an EJB's home or component interface.

In general, you should investigate which exceptions are causing your beans to be destroyed as they may be hurting performance and may indicate problem with the EJB or a resource used by the EJB.

Pool Timeout Ratio

The pool timeout ratio is a ratio of requests that have timed out waiting for a bean from the pool to the total number of requests made:

Pool Timeout Ratio = (Pool Total Timeout Count / Pool Total Access Count) * 100

A high pool timeout ratio could be indicative of an improperly sized free pool. Increasing the maximum size of your free pool via the max-beans-in-free-pool setting will increase the number of bean instances available to service requests and may reduce your pool timeout ratio.

Another factor affecting the number of pool timeouts is the configured transaction timeout for your bean. The maximum amount of time a thread will wait for a bean from the pool is equal to the default transaction timeout for the bean. Increasing the trans-timeout-seconds setting in your weblogic-ejb-jar.xml file will give threads more time to wait for a bean instance to become available.

Users should exercise caution when increasing this value, however, since doing so may cause threads to wait longer for a bean and threads are a valuable server resource. Also, request time might increase because a request will wait longer before timing out.

Transaction Rollback Ratio

The transaction rollback ratio is the ratio of transactions that have rolled back to the number of total transactions involving the EJB:

Transaction Rollback Ratio = (Transaction Total Rollback Count / Transaction Total Count) * 100

Begin investigating a high transaction rollback ratio by examining the Transaction Timeout Ratio reported in the Administration Console. If the transaction timeout ratio is higher than you expect, try to address the timeout problem first.

An unexpectedly high transaction rollback ratio could be caused by a number of things. We recommend investigating the cause of transaction rollbacks to find potential problems with your application or a resource used by your application.

Transaction Timeout Ratio

The transaction timeout ratio is the ratio of transactions that have timed out to the total number of transactions involving an EJB:

Transaction Timeout Ratio = (Transaction Total Timeout Count / Transaction Total Count) * 100

A high transaction timeout ratio could be caused by the wrong transaction timeout value. For example, if your transaction timeout is set too low, you may be timing out transactions before the thread is able to complete the necessary work. Increasing your transaction timeout value may reduce the number of transaction timeouts.

You should exercise caution when increasing this value, however, since doing so can cause threads to wait longer for a resource before timing out. Also, request time might increase because a request will wait longer before timing out.

A high transaction timeout ratio could be caused by a number of things such as a bottleneck for a server resource. We recommend tracing through your transactions to investigate what is causing the timeouts so the problem can be addressed.

Using the JDT Compiler

The JDT compiler can provide improved performance as compared to Javac. For this release:

- Both JDT and Javac is supported in the EJB container. JDT is the default option.

- You can set up to use different compilers in appc and WLS. For:

- appc, use -compiler, such as -java weblogic.appc -compiler javac ...

- WLS, use the ejb-container tag in config.xml file. For example:
<ejb-container>

<java-compiler>jdt</java-compiler>

</ejb-container>

If you use JDT in appc, only the -keepgenerated and -forceGeneration command line options are currently supported. These options have the same meaning as when using Javac.

11 Tuning Message-Driven Beans

This chapter provides tuning and best practice information for Message-Driven Beans (MDBs).

- Use Transaction Batching

- MDB Thread Management

- Best Practices for Configuring and Deploying MDBs Using Distributed Topics

- Using MDBs with Foreign Destinations

- Token-based Message Polling for Transactional MDBs Listening on Queues/Topics

- Compatibility for WLS 10.0 and Earlier-style Polling

Use Transaction Batching

MDB transaction batching allows several JMS messages to be processed in one container managed transaction. Batching amortizes the cost of transactions over multiple messages and when used appropriately, can reduce or even eliminate the throughput difference between 2PC and 1PC processing. See "Transaction Batching of MDBs" in Oracle Fusion Middleware Programming Message-Driven Beans for Oracle WebLogic Server.

- Using batching may require reducing the number of concurrent MDB instances. If too many MDB instances are available, messages may be processed in parallel rather than in a batch. See MDB Thread Management.

- While batching generally increases throughput, it may also increase latency (the time it takes for an individual message to complete its MDB processing).

MDB Thread Management

Thread management for MDBs is described in terms of concurrency—the number of MDB instances that can be active at the same time. The following sections provide information on MDB concurrency:

- Determining the Number of Concurrent MDBs

- Selecting a Concurrency Strategy

- Thread Utilization When Using WebLogic Destinations

- Limitations for Multi-threaded Topic MDBs

Determining the Number of Concurrent MDBs

Table 11-1 provides information on how to determine the number of concurrently running MDB instances for a server instance.

Table 11-1 Determining Concurrency for WebLogic Server MDBs

Type of work manager or execute queue

Threads

Default work manager or unconstrained work manager

varies due to self-tuning, up to Min(max-beans-in-free-pool,16)

Default work manager with self-tuning disabled

Min(default-thread-pool-size/2+1, max-beans-in-free-pool)

This is also the default thread pool concurrency algorithm for WebLogic Server 8.1

Custom execute queue

Min(execute-queue-size, max-beans-in-free-pool)

Custom work manager with constraint

varies due to self-tuning, between min-thread-constraint and Min(max-threads-constraint, max-beans-in-free-pool)

Transactional WebLogic MDBs use a synchronous polling mechanism to retrieve messages from JMS destinations if they are either: A) listening to non-WebLogic queues; or B) listening to a WebLogic queue and transaction batching is enabled. See Token-based Message Polling for Transactional MDBs Listening on Queues/Topics.

Selecting a Concurrency Strategy

The following section provides general information on selecting a concurrency strategy for your applications:

Note:

Every application is unique, select a concurrency strategy based on how your application performs in its environment.

- In most situations, if the message stream has bursts of messages, using an unconstrained work manager with a high fair share is adequate. Once the messages in a burst are handled, the threads are returned to the self-tuning pool.

- In most situations, if the message arrival rate is high and constant or if low latency is required, it makes sense to reserve threads for MDBs. You can reserve threads by either specifying a work manager with a min-threads-constraint or by using a custom execute queue.

- If you migrate WebLogic Server 8.1 applications that have custom MDB execute queues, you can:

- Continue to use a custom MDB execute queue, see Appendix A, "Using the WebLogic 8.1 Thread Pool Model."

- Convert the MDB execute queue to a custom work manager that has a configured max-threads-constraint parameter and a high fair share setting.

Note:

You must configure the max-threads-constraint parameter to override the default concurrency of 16.

- In WebLogic Server 8.1, you could increase the size of the default execute queue knowing that a larger default pool means a larger maximum MDB concurrency. Default thread pool MDBs upgraded to WebLogic Server 9.0 will have a fixed maximum of 16. To achieve MDB concurrency numbers higher than 16, you will need to create a custom work manager or custom execute queue. See Table 11-1.

Thread Utilization When Using WebLogic Destinations

The following section provides information on how threads are allocated when WebLogic Server interoperates with WebLogic destinations.

- Non-transactional WebLogic MDBs allocate threads from the thread-pool designated by the dispatch-policy as needed when there are new messages to be processed. If the MDB has successfully connected to its source destination, but there are no messages to be processed, then the MDB will use no threads.

- Transactional WebLogic MDBs with transaction batching disabled work the same as non-transactional MDBs except for Topic MDBs with a Topic Messages Distribution Mode of Compatibility (the default), in which case the MDB always limits the thread pool size to 1.

- The behavior of transactional MDBs with transaction batching enabled depends on whether the MDB is listening on a topic or a queue:

- MDBs listening on topics: — Each deployed MDB uses a dedicated daemon polling thread that is created in Non-Pooled Threads thread group.

- Topic Messages Distribution Mode = Compatibility: Each deployed MDB uses a dedicated daemon polling thread that is created in the Non-Pooled Threads thread group.

- Topic Messages Distribution Mode = One-Copy-Per-Server or One-Copy-Per-Application: Same as queues.

- MDBs listening on queues — Instead of a dedicated thread, each deployed MDB uses a token-based, synchronous polling mechanism that always uses at least one thread from the dispatch-policy. See Token-based Message Polling for Transactional MDBs Listening on Queues/Topics.

For information on how threads are allocated when WebLogic Server interoperates with MDBs that consume from Foreign destinations, see Thread Utilization for MDBs that Process Messages from Foreign Destinations.

Limitations for Multi-threaded Topic MDBs

When the topicMessagesDistributionMode is Compatibility, the default behavior for non-transactional topic MDBs is to multi-thread the message processing. In this situation, the MDB container fails to provide reproducible behavior when the topic is not a WebLogic JMS Topic, such as unexpected exceptions and acknowledgement of messages that have not yet been processed. For example, if an application throws a RuntimeException from onmessage, the container may still acknowledge the message. Oracle recommends setting max-beans-in-free-pool to a value of 1 in the deployment descriptor to prevent multi-threading in topic MDBs when the topic is a foreign vendor topic (not a WebLogic JMS topic).

Caution:

Non-transactional Foreign Topics: Oracle recommends explicitly setting max-beans-in-free-pool to 1 for non-transactional MDBs that work with foreign (non-WebLogic) topics. Failure to do so may result in lost messages in the event of certain failures, such as the MDB application throwing Runtime or Error exceptions.

Unit-of-Order: Oracle recommends explicitly setting max-beans-in-free-pool to 1 for non-transactional Compatibility mode MDBs that consume from a WebLogic JMS topic and process messages that have a WebLogic JMS Unit-of-Order value. Unit-of-Order messages in this use case may not be processed in order unless max-beans-in-free-pool is set to 1.

Transactional MDBs automatically force concurrency to 1 regardless of the max-beans-in-free-pool setting.

Best Practices for Configuring and Deploying MDBs Using Distributed Topics

Message-driven beans provide a number of application design and deployment options that offer scalability and high availability when using distributed topics. For more detailed information, see Configuring and Deploying MDBs Using Distributed Topics in Programming Message-Driven Beans for Oracle WebLogic Server.

Using MDBs with Foreign Destinations

Note:

The term "Foreign destination" in this context refers to destinations that are hosted by a non-WebLogic JMS provider. It does not refer to remote WebLogic destinations.

The following sections provide information on the behavior of WebLogic Server when using MDBs that consume messages from Foreign destinations:

- Concurrency for MDBs that Process Messages from Foreign Destinations

- Thread Utilization for MDBs that Process Messages from Foreign Destinations

Concurrency for MDBs that Process Messages from Foreign Destinations

The concurrency of MDBs that consume from destinations hosted by foreign providers (non-WebLogic JMS destinations) is determined using the same algorithm that is used for WebLogic JMS destinations.

Thread Utilization for MDBs that Process Messages from Foreign Destinations

The following section provides information on how threads are allocated when WebLogic Server interoperates with MDBs that process messages from foreign destinations:

- Non-transactional MDBs use a foreign vendor's thread, not a WebLogic Server thread. In this situation, the dispatch-policy is ignored except for determining concurrency.

- Transactional MDBs run in WebLogic Server threads, as follow:

- MDBs listening on topics — Each deployed MDB uses a dedicated daemon polling thread that is created in Non-Pooled Threads thread group.

- MDBs listening on queues — Instead of a dedicated thread, each deployed MDB uses a token-based, synchronous polling mechanism that always uses at least one thread from the dispatch-policy. See Token-based Message Polling for Transactional MDBs Listening on Queues/Topics

Token-based Message Polling for Transactional MDBs Listening on Queues/Topics

Transactional WebLogic MDBs use a synchronous polling mechanism to retrieve messages from JMS destinations if they are:

- Listening to non-WebLogic queues

- Listening to a WebLogic queue and transaction batching is enabled

- Listening to a WebLogic Topic where:

- Topic Messages Distribution Mode = One-Copy-Per-Server and transaction batching is enabled

- Topic Messages Distribution Mode = One-Copy-Per-Application and transaction batching is enabled

With synchronous polling, one or more WebLogic polling threads synchronously receive messages from the MDB's source destination and then invoke the MDB application's onMessage callback.

As of WebLogic 10.3, the polling mechanism changed to a token-based approach to provide better control of the concurrent poller thread count under changing message loads. In previous releases, the thread count ramp-up could be too gradual in certain use cases. Additionally, child pollers, once awoken, could not be ramped down and returned back to the pool for certain foreign JMS providers.

When a thread is returned to the thread pool with token-based polling, the thread's internal JMS consumer is closed rather than cached. This assures that messages will not be implicitly pre-fetched by certain foreign JMS Providers while there is no polling thread servicing the consumer.

In addition, each MDB maintains a single token that provides permission for a given poller thread to create another thread.

- On receipt of a message — A poller thread that already has the token or that is able to acquire the token because the token is not owned, wakes up an additional poller thread and gives the token to the new poller if the maximum concurrency has not yet been reached. If maximum concurrency has been reached, the poller thread simply releases the token (leaving it available to any other poller).

- On finding an empty queue/Topic — A poller tries to acquire the token and if successful will try to poll the queue periodically. If it fails to acquire the token, it returns itself back to the pool. This ensures that with an empty queue or topic, there is still at least one poller checking for messages.

Compatibility for WLS 10.0 and Earlier-style Polling

In WLS 10.0 and earlier, transactional MDBs with batching enabled created a dedicated polling thread for each deployed MDB. This polling thread was not allocated from the pool specified by dispatch-policy, it was an entirely new thread in addition to the all other threads running on the system. See Use Transaction Batching.

To override the token-based polling behavior and implement the WLS 10.0 and earlier behavior, you can either:

- At the server level, set the weblogic.mdb.message.81StylePolling system property to True to override the token-based polling behavior.

- At the MDB level, set the use81-style-polling element under message-driven-descriptor to override the token-based polling behavior. When using foreign transactional MDBs with the WLS 8.1-style polling flag, some foreign vendors require a permanently allocated thread per concurrent MDB instance. These threads are drawn from the pool specified by dispatch-policy and are not returned to the pool until the MDB is undeployed. Since these threads are not shared, the MDB can starve other resources in the same pool. In this situation, you may need to increase the number of threads in the pool. With the token-based polling approach for such foreign vendors, the thread's internal JMS message consumer is closed rather than cached to assure that messages will not be reserved by the destination for the specific consumer.

12 Tuning Data Sources

This chapter provides tips on how to get the best performance from your WebLogic data sources.

- Tune the Number of Database Connections

- Waste Not

- Use Test Connections on Reserve with Care

- Cache Prepared and Callable Statements

- Using Pinned-To-Thread Property to Increase Performance

- Database Listener Timeout under Heavy Server Loads

- Disable Wrapping of Data Type Objects

- Advanced Configurations for Oracle Drivers and Databases

- Use Best Design Practices

Tune the Number of Database Connections

A straightforward and easy way to boost performance of a data source in WebLogic Server applications is to set the value of Initial Capacity equal to the value for Maximum Capacity when configuring connection pools in your data source.

Creating a database connection is a relatively expensive process in any environment. Typically, a connection pool starts with a small number of connections. As client demand for more connections grow, there may not be enough in the pool to satisfy the requests. WebLogic Server creates additional connections and adds them to the pool until the maximum pool size is reached.

One way to avoid connection creation delays for clients using the server is to initialize all connections at server startup, rather than on-demand as clients need them. Set the initial number of connections equal to the maximum number of connections in the Connection Pool tab of your data source configuration. See "JDBC Data Source: Configuration: Connection Pool" in the Oracle WebLogic Server Administration Console Help. You will still need to determine the optimal value for the Maximum Capacity as part of your pre-production performance testing.

For more tuning information, see "Tuning Data Source Connection Pool Options" in Configuring and Managing JDBC Data Sources for Oracle WebLogic Server.

Waste Not

Another simple way to boost performance is to avoid wasting resources. Here are some situations where you can avoid wasting JDBC related resources:

- JNDI lookups are relatively expensive, so caching an object that required a looked-up in client code or application code avoids incurring this performance hit more than once.

- Once client or application code has a connection, maximize the reuse of this connection rather than closing and reacquiring a new connection. While acquiring and returning an existing creation is much less expensive than creating a new one, excessive acquisitions and returns to pools creates contention in the connection pool and degrades application performance.

- Don't hold connections any longer than is necessary to achieve the work needed. Getting a connection once, completing all necessary work, and returning it as soon as possible provides the best balance for overall performance.

Use Test Connections on Reserve with Care

When Test Connections on Reserve is enabled, the server instance checks a database connection prior to returning the connection to a client. This helps reduce the risk of passing invalid connections to clients.

However, it is a fairly expensive operation. Typically, a server instance performs the test by executing a full-fledged SQL query with each connection prior to returning it. If the SQL query fails, the connection is destroyed and a new one is created in its place. A new and optional performance tunable has been provided in WebLogic Server 9.x within this "test connection on reserve" feature. The new optional performance tunable in 9.x allows WebLogic Server to skip this SQL-query test within a configured time window of a prior successful client use (default is 10 seconds). When a connection is returned to the pool by a client, the connection is timestamped by WebLogic Server. WebLogic Server will then skip the SQL-query test if this particular connection is returned to a client within the time window. Once the time window expires, WebLogic Server will execute the SQL-query test. This feature can provide significant performance boosts for busy systems using "test connection on reserve".

Cache Prepared and Callable Statements

When you use a prepared statement or callable statement in an application or EJB, there is considerable processing overhead for the communication between the application server and the database server and on the database server itself. To minimize the processing costs, WebLogic Server can cache prepared and callable statements used in your applications. When an application or EJB calls any of the statements stored in the cache, WebLogic Server reuses the statement stored in the cache. Reusing prepared and callable statements reduces CPU usage on the database server, improving performance for the current statement and leaving CPU cycles for other tasks. For more details, see "Increasing Performance with the Statement Cache" in Configuring and Managing JDBC Data Sources for Oracle WebLogic Server.

Using the statement cache can dramatically increase performance, but you must consider its limitations before you decide to use it. For more details, see "Usage Restrictions for the Statement Cache" in Configuring and Managing WebLogic JDBC.

Using Pinned-To-Thread Property to Increase Performance

To minimize the time it takes for an application to reserve a database connection from a data source and to eliminate contention between threads for a database connection, you can add the Pinned-To-Thread property in the connection Properties list for the data source, and set its value to true.

In this release, the Pinned-To-Thread feature does not work with multi data sources, Oracle RAC, and IdentityPool. These features rely on the ability to return a connection to the connection pool and reacquire it if there is a connection failure or connection identity does not match

See "JDBC Data Source: Configuration: Connection Pool" in the Oracle WebLogic Server Administration Console Help.

Database Listener Timeout under Heavy Server Loads

In some situations where WebLogic Server is under heavy loads (high CPU utilization), the database listener may timeout and throw an exception while creating a new connection. To workaround this issue, increase the listener timeout on the database server. The following example is for an Oracle driver and database:

- The exception thrown is a ResourceDeadException and the driver exception was Socket read timed out.

- The workaround is to increase the timeout of the database server using the following:
sqlnet.ora: SQLNET.INBOUND_CONNECT_TIMEOUT=180

listener.ora: INBOUND_CONNECT_TIMEOUT_listener_name=180

Disable Wrapping of Data Type Objects

By default, data type objects for Array, Blob, Clob, NClob, Ref, SQLXML, and Struct, plus ParameterMetaData and ResultSetMetaData objects are wrapped with a WebLogic wrapper. You can disable wrapping, which can improve performance and allow applications to use native driver objects directly. See Using Unwrapped Data Type Objects in Configuring and Managing JDBC Data Sources for Oracle WebLogic Server.

Advanced Configurations for Oracle Drivers and Databases

Oracle provides advanced configuration options that can provide improved data source and driver performance when using Oracle drivers and databases. Options include proxy authentication, setting credentials on a connection, connection harvesting, and labeling connections. See "Advanced Configurations for Oracle Drivers and Databases" in Configuring and Managing JDBC Data Sources for Oracle WebLogic Server.

Use Best Design Practices

Most performance gains or losses in a database application is not determined by the application language, but by how the application is designed. The number and location of clients, size and structure of DBMS tables and indexes, and the number and types of queries all affect application performance. See "Designing Your Application for Best Performance" in Programming JDBC for Oracle WebLogic Server.

13 Tuning Transactions

This chapter provides background and tuning information for transaction optimization.

- Logging Last Resource Transaction Optimization

- Read-only, One-Phase Commit Optimizations

Logging Last Resource Transaction Optimization

The Logging Last Resource (LLR) transaction optimization through JDBC data sources safely reduces the overhead of two-phase transactions involving database inserts, updates, and deletes. Two phase transactions occur when two different resources participate in the same global transaction (global transactions are often referred to as "XA" or "JTA" transactions). Consider the following:

- Typical two-phase transactions in JMS applications usually involve both a JMS server and a database server. The LLR option can as much as double performance compared to XA.

- The safety of the JDBC LLR option contrasts with well known but less-safe XA optimizations such as "last-agent", "last-participant", and "emulate-two-phase-commit" that are available from other vendors as well as WebLogic.

- JDBC LLR works by storing two-phase transaction records in a database table rather than in the transaction manager log (the TLOG).

See "Logging Last Resource Transaction Optimization" in Programming JTA for Oracle WebLogic Server.

LLR Tuning Guidelines

The following section provides tuning guidelines for LLR:

- Oracle recommends that you read and understand "Logging Last Resource Transaction Optimization" in Programming JTA for Oracle WebLogic Server and "Programming Considerations and Limitations for LLR Data Sources" in Configuring and Managing JDBC Data Sources for Oracle WebLogic Server. LLR has a number of important administration and design implications.

- JDBC LLR generally improves performance of two-phase transactions that involve SQL updates, deletes, or inserts.

- LLR generally reduces the performance of two-phase transactions where all SQL operations are read-only (just selects).

- JDBC LLR pools provide no performance benefit to WebLogic JDBC stores. WebLogic JDBC stores are fully transactional but do not use JTA (XA) transactions on their internal JDBC connections.

- Consider using LLR instead of the less safe "last-agent" optimization for connectors, and the less safe "emulate-two-phase-commit" option for JDBC connection pools (formerly known as the "enable two-phase commit" option for pools that use non-XA drivers).

- On Oracle databases, heavily used LLR tables may become fragmented over time, which can lead to unused extents. This is likely due to the highly transient nature of the LLR table's data. To help avoid the issue, set PCT_FREE to 5 and PCT_USED to 95 on the LLR table. Also periodically defragment using the ALTER TABLESPACE [tablespace-name] COALESCE command.

Read-only, One-Phase Commit Optimizations

When resource managers, such as the Oracle Database (including Oracle AQ and Oracle RAC), provide read-only optimizations, Oracle WebLogic can provide a read-only, one-phase commit optimization that provides a number of benefits – even when enabling multiple connections of the same XA transactions – such as eliminating XAResource.prepare network calls and transaction log writes, both in Oracle WebLogic and in the resource manager.

See "Read-only, One-Phase Commit Optimizations" in Programming JTA for Oracle WebLogic Server.

14 Tuning WebLogic JMS

This chapter explains how to get the most out of your applications by implementing the administrative performance tuning features available with WebLogic JMS.

- JMS Performance & Tuning Check List

- Handling Large Message Backlogs

- Cache and Re-use Client Resources

- Tuning Distributed Queues

- Tuning Topics

- Tuning for Large Messages

- Defining Quota

- Blocking Senders During Quota Conditions

- Tuning MessageMaximum

- Setting Maximum Message Size for Network Protocols

- Compressing Messages

- Paging Out Messages To Free Up Memory

- Controlling the Flow of Messages on JMS Servers and Destinations

- Handling Expired Messages

- Tuning Applications Using Unit-of-Order

- Using One-Way Message Sends

- Tuning the Messaging Performance Preference Option

- Client-side Thread Pools

- Best Practices for JMS .NET Client Applications

JMS Performance & Tuning Check List

The following section provides a checklist of items to consider when tuning WebLogic JMS:

- Always configure quotas, see Defining Quota.

- Verify that default paging settings apply to your needs, see Paging Out Messages To Free Up Memory.. Paging lowers performance but may be required if JVM memory is insufficient.

- Avoid large message backlogs. See Handling Large Message Backlogs.

- Create and use custom connection factories with all applications instead of using default connection factories, including when using MDBs. Default connection factories are not tunable, while custom connection factories provide many options for performance tuning.

- Write applications so that they cache and re-use JMS client resources, including JNDI contexts and lookups, and JMS connections, sessions, consumers, or producers. These resources are relatively expensive to create. For information on detecting when caching is needed, as well as on built-in pooling features, see Cache and Re-use Client Resources.

- For asynchronous consumers and MDBs, tune MessagesMaximum on the connection factory. Increasing MessagesMaximum can improve performance, decreasing MessagesMaximum to its minimum value can lower performance, but helps ensure that messages do not end up waiting for a consumer that's already processing a message. See Tuning MessageMaximum.

- Avoid single threaded processing when possible. Use multiple concurrent producers and consumers and ensure that enough threads are available to service them.

- Tune server-side applications so that they have enough instances. Consider creating dedicated thread pools for these applications. See Tuning Message-Driven Beans.

- For client-side applications with asynchronous consumers, tune client-side thread pools using Client-side Thread Pools.

- Tune persistence as described in Tuning the WebLogic Persistent Store. In particular, it's normally best for multiple JMS servers, destinations, and other services to share the same store so that the store can aggregate concurrent requests into single physical I/O requests, and to reduce the chance that a JTA transaction spans more than one store. Multiple stores should only be considered once it's been established that the a single store is not scaling to handle the current load.

- If you have large messages, see Tuning for Large Messages.

- Prevent unnecessary message routing in a cluster by carefully configuring connection factory targets. Messages potentially route through two servers, as they flow from a client, through the client's connection host, and then on to a final destination. For server-side applications, target connection factories to the cluster. For client-side applications that work with a distributed destination, target connection factories only to servers that host the distributed destinations members. For client-side applications that work with a singleton destination, target the connection factory to the same server that hosts the destination.

- If JTA transactions include both JMS and JDBC operations, consider enabling the JDBC LLR optimization. LLR is a commonly used safe "ACID" optimization that can lead to significant performance improvements, with some drawbacks. See Tuning Transactions.

- If you are using Java clients, avoid thin Java clients except when a small jar size is more important than performance. Thin clients use the slower IIOP protocol even when T3 is specified so use a full java client instead. See Programming Stand-alone Clients for Oracle WebLogic Server.

- Tune JMS Store-and-Forward according to Tuning WebLogic JMS Store-and-Forward.

- Tune a WebLogic Messaging Bridge according Tuning WebLogic Message Bridge.

- If you are using non-persistent non-transactional remote producer clients, then consider enabling one-way calls. See Using One-Way Message Sends.

- Consider using JMS distributed queues. See "Using Distributed Queues" in Programming JMS for Oracle WebLogic Server.

- If you are already using distributed queues, see Tuning Distributed Queues.

- Consider using advanced distributed topic features (PDTs). See Developing Advanced Pub/Sub Applications in Programming JMS for Oracle WebLogic Server.

- If your applications use Topics, see Tuning Topics.

- Avoid configuring sorted destinations, including priority sorted destinations. FIFO or LIFO destinations are the most efficient. Destination sorting can be expensive when there are large message backlogs, even a backlog of a few hundred messages can lower performance.

- Use careful selector design. See "Filtering Messages" in Programming JMS for Oracle WebLogic Server.

- Run applications on the same WebLogic Servers that are also hosting destinations. This eliminates networking and some or all marshalling overhead, and can heavily reduce network and CPU usage. It also helps ensure that transactions are local to a single server. This is one of the major advantages of using an application server's embedded messaging.

Handling Large Message Backlogs

When message senders inject messages faster than consumers, messages accumulate into a message backlog. Large backlogs can be problematic for a number of reasons, for example:

- Indicates consumers may not be capable of handling the incoming message load, are failing, or are not properly load balanced across a distributed queue.

- Can lead to out-of-memory on the server, which in turn prevents the server from doing any work.

- Can lead to high garbage collection (GC) overhead. A JVM's GC overhead is partially proportional to the number of live objects in the JVM.

Improving Message Processing Performance

One area for investigation is to improve overall message processing performance. Here are some suggestions:

- Follow the JMS tuning recommendations as described in JMS Performance & Tuning Check List.

- Check for programming errors in newly developed applications. In particular, ensure that non-transactional consumers are acknowledging messages, that transactional consumers are committing transactions, that plain javax.jms applications called javax.jms.Connection.start(), and that transaction timeouts are tuned to reflect the needs of your particular application. Here are some symptoms of programming errors: consumers are not receiving any messages (make sure they called start()), high "pending" counts for queues, already processed persistent messages re-appearing after a shutdown and restart, and already processed transactional messages re-appearing after a delay (the default JTA timeout is 30 seconds, default transacted session timeout is one hour).

- Check WebLogic statistics for queues that are not being serviced by consumers. If you're having a problem with distributed queues, see Tuning Distributed Queues.

- Check WebLogic statistics for topics with high pending counts. This usually indicates that there are topic subscriptions that are not being serviced. There may be a slow or unresponsive consumer client that's responsible for processing the messages, or it's possible that a durable subscription may no longer be needed and should be deleted, or the messages may be accumulating due to delayed distributed topic forwarding. You can check statistics for individual durable subscriptions on the administration console. A durable subscription with a large backlog may have been created by an application but never deleted. Unserviced durable subscriptions continue to accumulate topic messages until they are either administratively destroyed, or unsubscribed by a standard JMS client.

- Understand distributed topic behavior when not all members are active. In distributed topics, each produced message to a particular topic member is forwarded to each remote topic member. If a remote topic member is unavailable then the local topic member will store each produced message for later forwarding. Therefore, if a topic member is unavailable for a long period of time, then large backlogs can develop on the active members. In some applications, this backlog can be addressed by setting expiration times on the messages. See Defining a Message Expiration Policy.

- In certain applications it may be fine to automatically delete old unprocessed messages. See Handling Expired Messages.

- For transactional MDBs, consider using MDB transaction batching as this can yield a 5 fold improvement in some use cases.

- Leverage distributed queues and add more JVMs to the cluster (in order to add more distributed queue member instances). For example, split a 200,000 message backlog across 4 JVMs at 50,000 messages per JVM, instead of 100,000 messages per JVM.

- For client applications, use asynchronous consumers instead of synchronous consumers when possible. Asynchronous consumers can have a significantly lower network overhead, lower latency, and do not block a thread while waiting for a message.

- For synchronous consumer client applications, consider: enabling prefetch, using CLIENT_ACKNOWLEDGE to enable acknowledging multiple consumed messages at a time, and using DUPS_OK_ACKNOWLEDGE instead of AUTO_ACKNOWLEDGE.

- For asynchronous consumer client applications, consider using DUPS_OK_ACKNOWLEDGE instead of AUTO_ACKNOWLEDGE.

- Leverage batching. For example, include multiple messages in each transaction, or send one larger message instead of many smaller messages.

- For non-durable subscriber client-side applications handling missing ("dropped") messages, investigate MULTICAST_NO_ACKNOWLEDGE. This mode broadcasts messages concurrently to subscribers over UDP multicast.

Controlling Message Production

Another area for investigation is to slow down or even stop message production. Here are some suggestions:

- Set lower quotas. See Defining Quota.

- Use fewer producer threads.

- Tune a sender blocking timeout that occurs during a quota condition, as described Blocking Senders During Quota Conditions.. The timeout is tunable on connection factory.

- Tune producer flow control, which automatically slows down producer calls under threshold conditions. See Controlling the Flow of Messages on JMS Servers and Destinations.

- Consider modifying the application to implement flow-control. For example, some applications do not allow producers to inject more messages until a consumer has successfully processed the previous batch of produced messages (a windowing protocol). Other applications might implement a request/reply algorithm where a new request isn't submitted until the previous reply is received (essentially a windowing protocol with a window size of 1). In some cases, JMS tuning is not required as the synchronous flow from the RMI/EJB/Servlet is adequate.

Drawbacks to Controlling Message Production

Slowing down or stopping message processing has at least two potential drawbacks:

- It puts back-pressure on the down-stream flow that is calling the producer. Sometimes the down-stream flow cannot handle this back-pressure, and a hard-to-handle backlog develops behind the producer. The location of the backlog depends on what's calling the producer. For example, if the producer is being called by a servlet, the backlog might manifest as packets accumulating on the incoming network socket or network card.

- Blocking calls on server threads can lead to thread-starvation, too many active threads, or even dead-locks. Usually the key to address this problem is to ensure that the producer threads are running in a size limited dedicated thread pool, as this ensures that the blocking threads do not interfere with activity in other thread pools. For example, if an EJB or servlet is calling a "send" that might block for a significant time: configure a custom work manager with a max threads constraint, and set the dispatch-policy of the EJB/servlet to reference this work-manager.

Cache and Re-use Client Resources

JMS client resources are relatively expensive to create in comparison to sending and receiving messages. These resources should be cached or pooled for re-use rather than recreating them with each message. They include contexts, destinations, connection factories, connections, sessions, consumers, or producers.

In addition, it is important for applications to close contexts, connections, sessions, consumers, or producers once they are completely done with these resources. Failing to close unused resources leads to a memory leak, which lowers overall JVM performance and eventually may cause the JVM to fail with an out-of-memory error. Be aware that JNDI contexts have close() method, and that closing a JMS connection automatically efficiently closes all sessions, consumers, and producers created using the connection.

For server-side applications, WebLogic automatically wraps and pools JMS resources that are accessed using a resource reference. See "Enhanced Support for Using WebLogic JMS with EJBs and Servlets" in Programming JMS for Oracle WebLogic Server. This pooling code can be inefficient at pooling producers if the target destination changes frequently, but there's a simple work-around: use anonymous producers by passing null for the destination when the application calls createProducer() and then instead pass the desired destination into each send call.

- To check for heavy JMS resource allocation or leaks, you can monitor mbean stats and/or use your particular JVM's built in facilities. You can monitor mbean stats using the console, WLST, or java code.

- Check JVM heap statistics for memory leaks or unexpectedly high allocation counts (called a JRA profile in JRockit).

- Similarly, check WebLogic statistics for memory leaks or unexpectedly high allocation counts.

Tuning Distributed Queues

If produced messages are failing to load balance evenly across all distributed queue members, you may wish to change the configuration of your producer connection factories to disable server affinity (enabled by default).

Once created, a JMS consumer remains pinned to a particular queue member. This can lead to situations where consumers are not evenly load balanced across all distributed queue members, particularly if new members become available after all consumers have been initialized. If consumers fail to load balance evenly across all distributed queue members, the best option is to use an MDB that's targeted to a cluster designed to process the messages. WebLogic MDBs automatically ensure that all distributed queue members are serviced. If MDBs are not an option, here are some suggestions to improve consumer load balancing:

- Ensure that your application is creating enough consumers and the consumer's connection factory is tuned using the available load balancing options. In particular, consider disabling the default server affinity setting.)

- Change applications to periodically close and recreate consumers. This forces consumers to re-load balance.

- Consume from individual queue members instead of from the distributed queues logical name. Each distributed queue member is individually advertised in JNDI as jms-server-name@distributed-destination-jndi-name.

- Configure the distributed queue to enable forwarding. Distributed queue forwarding automatically internally forwards messages that have been idled on a member destination without consumers to a member that has consumers. This approach may not be practical for high message load applications.

Note:

Queue forwarding is not compatible with the WebLogic JMS Unit-of-Order feature, as it can cause messages to be delivered out of order.

See "Using Distributed Destinations" in Programming JMS for Oracle WebLogic Server and Configuring Advanced JMS System Resources in Configuring and Managing JMS for Oracle WebLogic Server.

Tuning Topics

The following section provides information on how to tune WebLogic Topics:

- You may want to convert singleton topics to distributed topics. A distributed topic with a Partitioned policy generally outperforms the Replicated policy choice.

- Oracle highly recommends leveraging MDBs to process Topic messages, especially when working with Distributed Topics. MDBs automate the creation and servicing of multiple subscriptions and also provide high scalability options to automatically distribute the messages for a single subscription across multiple Distributed Topic members.

- There is a Sharable subscription extension that allows messages on a single topic subscription to be processed in parallel by multiple subscribers on multiple JVMs. WebLogic MDBs leverage this feature when they are not in Compatibility mode.

- If produced messages are failing to load balance evenly across the members of a Partitioned Distributed Topic, you may need to change the configuration of your producer connection factories to disable server affinity (enabled by default).

- Before using any of these previously mentioned advanced features, Oracle recommends fully reviewing the following related documentation:

- "Configuring and Deploying MDBs Using Distributed Topics" in Programming Message-Driven Beans for Oracle WebLogic Server

- "Developing Advanced Pub/Sub Applications" in Configuring and Managing JMS for Oracle WebLogic Server

- "Advanced Programming with Distributed Destinations Using the JMS Destination Availability Helper API" in Configuring and Managing JMS for Oracle WebLogic Server

Tuning for Large Messages

The following sections provide information on how to improve JMS performance when handling large messages:

- Tuning MessageMaximum

- Setting Maximum Message Size for Network Protocols

- Compressing Messages

- Paging Out Messages To Free Up Memory

Defining Quota

It is highly recommended to always configure message count quotas. Quotas help prevent large message backlogs from causing out-of-memory errors, and WebLogic JMS does not set quotas by default.

There are many options for setting quotas, but in most cases it is enough to simply set a Messages Maximum quota on each JMS Server rather than using destination level quotas. Keep in mind that each current JMS message consumes JVM memory even when the message has been paged out, because paging pages out only the message bodies but not message headers. A good rule of thumb for queues is to assume that each current JMS message consumes 512 bytes of memory. A good rule of thumb for topics is to assume that each current JMS message consumes 256 bytes of memory plus an additional 256 bytes of memory for each subscriber that hasn't acknowledged the message yet. For example, if there are 3 subscribers on a topic, then a single published message that hasn't been processed by any of the subscribers consumes 256 + 256*3 = 1024 bytes even when the message is paged out. Although message header memory usage is typically significantly less than these rules of thumb indicate, it is a best practice to make conservative estimates on memory utilization.

In prior releases, there were multiple levels of quotas: destinations had their own quotas and would also have to compete for quota within a JMS server. In this release, there is only one level of quota: destinations can have their own private quota or they can compete with other destinations using a shared quota.

In addition, a destination that defines its own quota no longer also shares space in the JMS server's quota. Although JMS servers still allow the direct configuration of message and byte quotas, these options are only used to provide quota for destinations that do not refer to a quota resource.

Quota Resources

A quota is a named configurable JMS module resource. It defines a maximum number of messages and bytes, and is then associated with one or more destinations and is responsible for enforcing the defined maximums. Multiple destinations referring to the same quota share available quota according to the sharing policy for that quota resource.

Quota resources include the following configuration parameters:

Table 14-1 Quota Parameters

Attribute

Description

Bytes Maximum and Messages Maximum

The Messages Maximum/Bytes Maximum parameters for a quota resource defines the maximum number of messages and/or bytes allowed for that quota resource. No consideration is given to messages that are pending; that is, messages that are in-flight, delayed, or otherwise inhibited from delivery still count against the message and/or bytes quota.

Quota Sharing

The Shared parameter for a quota resource defines whether multiple destinations referring to the same quota resource compete for resources with each other.

Quota Policy

The Policy parameter defines how individual clients compete for quota when no quota is available. It affects the order in which send requests are unblocked when the Send Timeout feature is enabled on the connection factory, as described in Tuning for Large Messages.

For more information about quota configuration parameters, see QuotaBean in the Oracle WebLogic Server MBean Reference. For instructions on configuring a quota resource using the Administration Console, see "Create a quota for destinations" in the Oracle WebLogic Server Administration Console Help.

Destination-Level Quota

Destinations no longer define byte and messages maximums for quota, but can use a quota resource that defines these values, along with quota policies on sharing and competition.

The Quota parameter of a destination defines which quota resource is used to enforce quota for the destination. This value is dynamic, so it can be changed at any time. However, if there are unsatisfied requests for quota when the quota resource is changed, then those requests will fail with a javax.jms.ResourceAllocationException.

Note:

Outstanding requests for quota will fail at such time that the quota resource is changed. This does not mean changes to the message and byte attributes for the quota resource, but when a destination switches to a different quota.

JMS Server-Level Quota

In some cases, there will be destinations that do not configure quotas. JMS Server quotas allow JMS servers to limit the resources used by these quota-less destinations. All destinations that do not explicitly set a value for the Quota attribute share the quota of the JMS server where they are deployed. The behavior is exactly the same as if there were a special Quota resource defined for each JMS server with the Shared parameter enabled.

The interfaces for the JMS server quota are unchanged from prior releases. The JMS server quota is entirely controlled using methods on the JMSServerMBean. The quota policy for the JMS server quota is set by the Blocking Send Policy parameter on a JMS server, as explained in Specifying a Blocking Send Policy on JMS Servers. It behaves just like the Policy setting of any other quota.

Blocking Senders During Quota Conditions

- Defining a Send Timeout on Connection Factories

- Specifying a Blocking Send Policy on JMS Servers

Defining a Send Timeout on Connection Factories

Blocking producers during quota conditions (by defining a send timeout) can dramatically improve the performance of applications and benchmarks that continuously retry message sends on quota failures. The Send Timeout feature provides more control over message send operations by giving message produces the option of waiting a specified length of time until space becomes available on a destination. For example, if a producer makes a request and there is insufficient space, then the producer is blocked until space becomes available, or the operation times out. See Controlling the Flow of Messages on JMS Servers and Destinations for another method of flow control.

To use the Administration Console to define how long a JMS connection factory will block message requests when a destination exceeds its maximum quota.

1. Follow the directions for navigating to the JMS Connection Factory: Configuration: Flow Control page in "Configure message flow control" in the Oracle WebLogic Server Administration Console Help.

2. In the Send Timeout field, enter the amount of time, in milliseconds, a sender will block messages when there is insufficient space on the message destination. Once the specified waiting period ends, one of the following results will occur:

- If sufficient space becomes available before the timeout period ends, the operation continues.

- If sufficient space does not become available before the timeout period ends, you receive a resource allocation exception.
If you choose not to enable the blocking send policy by setting this value to 0, then you will receive a resource allocation exception whenever sufficient space is not available on the destination.

For more information about the Send Timeout field, see "JMS Connection Factory: Configuration: Flow Control" in the Oracle WebLogic Server Administration Console Help.

3. Click Save.

Specifying a Blocking Send Policy on JMS Servers

The Blocking Send policies enable you to define the JMS server's blocking behavior on whether to deliver smaller messages before larger ones when multiple message producers are competing for space on a destination that has exceeded its message quota.

To use the Administration Console to define how a JMS server will block message requests when its destinations are at maximum quota.

1. Follow the directions for navigating to the JMS Server: Configuration: Thresholds and Quotas page of the Administration Console in "Configure JMS server thresholds and quota" in Oracle WebLogic Server Administration Console Help.

2. From the Blocking Send Policy list box, select one of the following options:

- FIFO — All send requests for the same destination are queued up one behind the other until space is available. No send request is permitted to complete when there another send request is waiting for space before it.

- Preemptive — A send operation can preempt other blocking send operations if space is available. That is, if there is sufficient space for the current request, then that space is used even if there are previous requests waiting for space.

- For more information about the Blocking Send Policy field, see "JMS Server: Configuration: Thresholds and Quota" in the Oracle WebLogic Server Administration Console Help.

3. Click Save.

Tuning MessageMaximum

WebLogic JMS pipelines messages that are delivered to asynchronous consumers (otherwise known as message listeners) or prefetch-enabled synchronous consumers. This action aids performance because messages are aggregated when they are internally pushed from the server to the client. The messages backlog (the size of the pipeline) between the JMS server and the client is tunable by configuring the MessagesMaximum setting on the connection factory. See "Asynchronous Message Pipeline" in Programming JMS for Oracle WebLogic Server.

In some circumstances, tuning the MessagesMaximum parameter may improve performance dramatically, such as when the JMS application defers acknowledges or commits. In this case, Oracle suggests setting the MessagesMaximum value to:

2 * (ack or commit interval) + 1

For example, if the JMS application acknowledges 50 messages at a time, set the MessagesMaximum value to 101.

Tuning MessageMaximum Limitations

Tuning the MessagesMaximum value too high can cause:

- Increased memory usage on the client.

- Affinity to an existing client as its pipeline fills with messages. For example: If MessagesMaximum has a value of 10,000,000, the first consumer client to connect will get all messages that have already arrived at the destination. This condition leaves other consumers without any messages and creates an unnecessary backlog of messages in the first consumer that may cause the system to run out of memory.

- Packet is too large exceptions and stalled consumers. If the aggregate size of the messages pushed to a consumer is larger than the current protocol's maximum message size (default size is 10 MB and is configured on a per WebLogic Server instance basis using the console and on a per client basis using the -Dweblogic.MaxMessageSize command line property), the message delivery fails.

Setting Maximum Message Size for Network Protocols

You may need to configure WebLogic clients in addition to the WebLogic Server instances, when sending and receiving large messages.

For most protocols, including T3, WLS limits the size of a network call to 10MB by default. If individual JMS message sizes exceed this limit, or if a set of JMS messages that is batched into the same network call exceeds this limit, this can lead to either “packet too large exceptions” and/or stalled consumers. Asynchronous consumers can cause multiple JMS messages to batch into the same network call, to control this batch size, see Tuning MessageMaximum Limitations.

To set the maximum message size on a server instance, tune the maximum message size for each supported protocol on a per protocol basis for each involved default channel or custom channel. In this context the word 'message' refers to all network calls over the given protocol, not just JMS calls.

To set the maximum message size on a client, use the following command line property:

-Dweblogic.MaxMessageSize

Note:

This setting applies to all WebLogic Server network packets delivered to the client, not just JMS related packets.

Compressing Messages

A message compression threshold can be set programmatically using a JMS API extension to the WLMessageProducer interface, or administratively by either specifying a Default Compression Threshold value on a connection factory or on a JMS SAF remote context. Compressed messages may actually inadvertently affect destination quotas since some message types actually grow larger when compressed

For instructions on configuring default compression thresholds using the Administration Console, see:

- Connection factories — "Configure default delivery parameters" in the Oracle WebLogic Server Administration Console Help.

- Store-and-Forward (SAF) remote contexts — "Configure SAF remote contexts" in the Oracle WebLogic Server Administration Console Help.

Once configured, message compression is triggered on producers for client sends, on connection factories for message receives and message browsing, or through SAF forwarding. Messages are compressed using GZIP. Compression only occurs when message producers and consumers are located on separate server instances where messages must cross a JVM boundary, typically across a network connection when WebLogic domains reside on different machines. Decompression automatically occurs on the client side and only when the message content is accessed, except for the following situations:

- Using message selectors on compressed XML messages can cause decompression, since the message body must be accessed in order to filter them. For more information on defining XML message selectors, see "Filtering Messages" in Programming JMS for Oracle WebLogic Server.

- Interoperating with earlier versions of WebLogic Server can cause decompression. For example, when using the Messaging Bridge, messages are decompressed when sent from the current release of WebLogic Server to a receiving side that is an earlier version of WebLogic Server.

On the server side, messages always remains compressed, even when they are written to disk.

Paging Out Messages To Free Up Memory

With the message paging feature, JMS servers automatically attempt to free up virtual memory during peak message load periods. This feature can greatly benefit applications with large message spaces. Message paging is always enabled on JMS servers, and so a message paging directory is automatically created without having to configure one. You can, however, specify a directory using the Paging Directory option, then paged-out messages are written to files in this directory.

In addition to the paging directory, a JMS server uses either a file store or a JDBC store for persistent message storage. The file store can be user-defined or the server's default store. Paged JDBC store persistent messages are copied to both the JDBC store as well as the JMS Server's paging directory. Paged file store persistent messages that are small are copied to both the file store as well as the JMS Server's paging directory. Paged larger file store messages are not copied into the paging directory. See Best Practices When Using Persistent Stores.

However, a paged-out message does not free all of the memory that it consumes, since the message header with the exception of any user properties, which are paged out along with the message body, remains in memory for use with searching, sorting, and filtering. Queuing applications that use selectors to select paged messages may show severely degraded performance as the paged out messages must be paged back in. This does not apply to topics or to applications that select based only on message header fields (such as CorrelationID). A good rule of thumb is to conservatively assume that messages each use 512 bytes of JVM memory even when paged out.

Specifying a Message Paging Directory

If a paging directory is not specified, then paged-out message bodies are written to the default \tmp directory inside the servername subdirectory of a domain's root directory. For example, if no directory name is specified for the default paging directory, it defaults to:

mw_home\user_projects\domains\domainname\servers\servername\tmp

where domainname is the root directory of your domain, typically c:\Oracle\Middleware\user_projects\domains\domainname, which is parallel to the directory in which WebLogic Server program files are stored, typically c:\Oracle\Middleware\wlserver_10.x.

To configure the Message Paging Directory attribute, see "Configure general JMS server properties" in Oracle WebLogic Server Administration Console Help.

Tuning the Message Buffer Size Option

The Message Buffer Size option specifies the amount of memory that will be used to store message bodies in memory before they are paged out to disk. The default value of Message Buffer Size is approximately one-third of the maximum heap size for the JVM, or a maximum of 512 megabytes. The larger this parameter is set, the more memory JMS will consume when many messages are waiting on queues or topics. Once this threshold is crossed, JMS may write message bodies to the directory specified by the Paging Directory option in an effort to reduce memory usage below this threshold.

It is important to remember that this parameter is not a quota. If the number of messages on the server passes the threshold, the server writes the messages to disk and evicts the messages from memory as fast as it can to reduce memory usage, but it will not stop accepting new messages. It is still possible to run out of memory if messages are arriving faster than they can be paged out. Users with high messaging loads who wish to support the highest possible availability should consider setting a quota, or setting a threshold and enabling flow control to reduce memory usage on the server.

Controlling the Flow of Messages on JMS Servers and Destinations

With the Flow Control feature, you can direct a JMS server or destination to slow down message producers when it determines that it is becoming overloaded. See Compressing Messages.

The following sections describe how flow control feature works and how to configure flow control on a connection factory.

- How Flow Control Works

- Configuring Flow Control

- Flow Control Thresholds

How Flow Control Works

Specifically, when either a JMS server or it's destinations exceeds its specified byte or message threshold, it becomes armed and instructs producers to limit their message flow (messages per second).

Producers will limit their production rate based on a set of flow control attributes configured for producers via the JMS connection factory. Starting at a specified flow maximum number of messages, a producer evaluates whether the server/destination is still armed at prescribed intervals (for example, every 10 seconds for 60 seconds). If at each interval, the server/destination is still armed, then the producer continues to move its rate down to its prescribed flow minimum amount.

As producers slow themselves down, the threshold condition gradually corrects itself until the server/destination is unarmed. At this point, a producer is allowed to increase its production rate, but not necessarily to the maximum possible rate. In fact, its message flow continues to be controlled (even though the server/destination is no longer armed) until it reaches its prescribed flow maximum, at which point it is no longer flow controlled.

Configuring Flow Control

Producers receive a set of flow control attributes from their session, which receives the attributes from the connection, and which receives the attributes from the connection factory. These attributes allow the producer to adjust its message flow.

Specifically, the producer receives attributes that limit its flow within a minimum and maximum range. As conditions worsen, the producer moves toward the minimum; as conditions improve; the producer moves toward the maximum. Movement toward the minimum and maximum are defined by two additional attributes that specify the rate of movement toward the minimum and maximum. Also, the need for movement toward the minimum and maximum is evaluated at a configured interval.

Flow Control options are described in following table:

Table 14-2 Flow Control Parameters

Attribute

Description

Flow Control Enabled

Determines whether a producer can be flow controlled by the JMS server.

Flow Maximum

The maximum number of messages per second for a producer that is experiencing a threshold condition.

If a producer is not currently limiting its flow when a threshold condition is reached, the initial flow limit for that producer is set to Flow Maximum. If a producer is already limiting its flow when a threshold condition is reached (the flow limit is less than Flow Maximum), then the producer will continue at its current flow limit until the next time the flow is evaluated.

Once a threshold condition has subsided, the producer is not permitted to ignore its flow limit. If its flow limit is less than the Flow Maximum, then the producer must gradually increase its flow to the Flow Maximum each time the flow is evaluated. When the producer finally reaches the Flow Maximum, it can then ignore its flow limit and send without limiting its flow.

Flow Minimum

The minimum number of messages per second for a producer that is experiencing a threshold condition. This is the lower boundary of a producer's flow limit. That is, WebLogic JMS will not further slow down a producer whose message flow limit is at its Flow Minimum.

Flow Interval

An adjustment period of time, defined in seconds, when a producer adjusts its flow from the Flow Maximum number of messages to the Flow Minimum amount, or vice versa.

Flow Steps

The number of steps used when a producer is adjusting its flow from the Flow Minimum amount of messages to the Flow Maximum amount, or vice versa. Specifically, the Flow Interval adjustment period is divided into the number of Flow Steps (for example, 60 seconds divided by 6 steps is 10 seconds per step).

Also, the movement (that is, the rate of adjustment) is calculated by dividing the difference between the Flow Maximum and the Flow Minimum into steps. At each Flow Step, the flow is adjusted upward or downward, as necessary, based on the current conditions, as follows:

The downward movement (the decay) is geometric over the specified period of time (Flow Interval) and according to the specified number of Flow Steps. (For example, 100, 50, 25, 12.5).

The movement upward is linear. The difference is simply divided by the number of Flow Steps.

For more information about the flow control fields, and the valid and default values for them, see "JMS Connection Factory: Configuration: Flow Control" in the Oracle WebLogic Server Administration Console Help.

Flow Control Thresholds

The attributes used for configuring bytes/messages thresholds are defined as part of the JMS server and/or its destination. Table 14-2 defines how the upper and lower thresholds start and stop flow control on a JMS server and/or JMS destination.

Table 14-3 Flow Control Threshold Parameters

Attribute

Description

Bytes/Messages Threshold High

When the number of bytes/messages exceeds this threshold, the JMS server/destination becomes armed and instructs producers to limit their message flow.

Bytes/Messages Threshold Low

When the number of bytes/messages falls below this threshold, the JMS server/destination becomes unarmed and instructs producers to begin increasing their message flow.

Flow control is still in effect for producers that are below their message flow maximum. Producers can move their rate upward until they reach their flow maximum, at which point they are no longer flow controlled.

For detailed information about other JMS server and destination threshold and quota fields, and the valid and default values for them, see the following pages in the Administration Console Online Help:

- "JMS Server: Configuration: Thresholds and Quotas"

- "JMS Queue: Configuration: Thresholds and Quotas"

- "JMS Topic: Configuration: Thresholds and Quotas"

Handling Expired Messages

The following sections describe two message expiration features, the message Expiration Policy and the Active Expiration of message, which provide more control over how the system searches for expired messages and how it handles them when they are encountered.

Active message expiration ensures that expired messages are cleaned up immediately. Moreover, expired message auditing gives you the option of tracking expired messages, either by logging when a message expires or by redirecting expired messages to a defined error destination.

- Defining a Message Expiration Policy

- Tuning Active Message Expiration

Defining a Message Expiration Policy

Use the message Expiration Policy feature to define an alternate action to take when messages expire. Using the Expiration Policy attribute on the Destinations node, an expiration policy can be set on a per destination basis. The Expiration Policy attribute defines the action that a destination should take when an expired message is encountered: discard the message, discard the message and log its removal, or redirect the message to an error destination.

Also, if you use JMS templates to configure multiple destinations, you can use the Expiration Policy field to quickly configure an expiration policy on all your destinations. To override a template's expiration policy for specific destinations, you can modify the expiration policy on any destination.

For instructions on configuring the Expiration Policy, click one of the following links:

- Configuring an Expiration Policy on Topics

- Configuring an Expiration Policy on Queues

- Configuring an Expiration Policy on Templates

- Defining an Expiration Logging Policy

Configuring an Expiration Policy on Topics

Follow these directions if you are configuring an expiration policy on topics without using a JMS template. Expiration policies that are set on specific topics will override the settings defined on a JMS template.

1. Follow the directions for navigating to the JMS Topic: Configuration: Delivery Failure page in "Configure topic message delivery failure options" in the Oracle WebLogic Server Administration Console Help.

2. From the Expiration Policy list box, select an expiration policy option.

- Discard — Expired messages are removed from the system. The removal is not logged and the message is not redirected to another location.

- Log — Removes expired messages and writes an entry to the server log file indicating that the messages were removed from the system. You define the actual information that will be logged in the Expiration Logging Policy field in next step.

- Redirect — Moves expired messages from their current location into the Error Destination defined for the topic.
For more information about the Expiration Policy options for a topic, see "JMS Topic: Configuration: Delivery Failure" in the Oracle WebLogic Server Administration Console Help.

3. If you selected the Log expiration policy in previous step, use the Expiration Logging Policy field to define what information about the message is logged.
For more information about valid Expiration Logging Policy values, see Defining an Expiration Logging Policy.

4. Click Save.

Configuring an Expiration Policy on Queues

Follow these directions if you are configuring an expiration policy on queues without using a JMS template. Expiration policies that are set on specific queues will override the settings defined on a JMS template.

1. Follow the directions for navigating to the JMS Queue: Configuration: Delivery Failure page in "Configure queue message delivery failure options" in the Oracle WebLogic Server Administration Console Help.

2. From the Expiration Policy list box, select an expiration policy option.

- Discard — Expired messages are removed from the system. The removal is not logged and the message is not redirected to another location.

- Log — Removes expired messages from the queue and writes an entry to the server log file indicating that the messages were removed from the system. You define the actual information that will be logged in the Expiration Logging Policy field described in the next step.

- Redirect — Moves expired messages from the queue and into the Error Destination defined for the queue.

- For more information about the Expiration Policy options for a queue, see "JMS Queue: Configuration: Delivery Failure" in the Oracle WebLogic Server Administration Console Help.

3. If you selected the Log expiration policy in the previous step, use the Expiration Logging Policy field to define what information about the message is logged.
For more information about valid Expiration Logging Policy values, see Defining an Expiration Logging Policy.

4. Click Save

Configuring an Expiration Policy on Templates

Since JMS templates provide an efficient way to define multiple destinations (topics or queues) with similar attribute settings, you can configure a message expiration policy on an existing template (or templates) for your destinations.

1. Follow the directions for navigating to the JMS Template: Configuration: Delivery Failure page in "Configure JMS template message delivery failure options" in the Oracle WebLogic Server Administration Console Help.

2. In the Expiration Policy list box, select an expiration policy option.

- Discard — Expired messages are removed from the messaging system. The removal is not logged and the message is not redirected to another location.

- Log — Removes expired messages and writes an entry to the server log file indicating that the messages were removed from the system. The actual information that is logged is defined by the Expiration Logging Policy field described in the next step.

- Redirect — Moves expired messages from their current location into the Error Destination defined for the destination.

- For more information about the Expiration Policy options for a template, see "JMS Template: Configuration: Delivery Failure" in the Oracle WebLogic Server Administration Console Help.

3. If you selected the Log expiration policy in Step 4, use the Expiration Logging Policy field to define what information about the message is logged.
For more information about valid Expiration Logging Policy values, see Defining an Expiration Logging Policy.

4. Click Save.

Defining an Expiration Logging Policy

The following section provides information on the expiration policy.

The Expiration Logging Policy parameter has been deprecated in this release of WebLogic Server. In its place, Oracle recommends using the Message Life Cycle Logging feature, which provide a more comprehensive view of the basic events that JMS messages will traverse through once they are accepted by a JMS server, including detailed message expiration data. For more information about message life cycle logging options, see "Message Life Cycle Logging" in Configuring and Managing JMS for Oracle WebLogic Server.

For example, you could specify one of the following values:

- JMSPriority, Name, Address, City, State, Zip

- %header%, Name, Address, City, State, Zip

- JMSCorrelationID, %properties%

The JMSMessageID field is always logged and cannot be turned off. Therefore, if the Expiration Policy is not defined (that is, none) or is defined as an empty string, then the output to the log file contains only the JMSMessageID of the message.

Expiration Log Output Format

When an expired message is logged, the text portion of the message (not including timestamps, severity, thread information, security identity, etc.) conforms to the following format:

<ExpiredJMSMessage JMSMessageId='$MESSAGEID' >
<HeaderFields Field1='Value1' [Field2='Value2'] … ] />
<UserProperties Property1='Value1' [Property='Value2'] … ] />
</ExpiredJMSMessage>

where $MESSAGEID is the exact string returned by Message.getJMSMessageID().

For example:

<ExpiredJMSMessage JMSMessageID='ID:P<851839.1022176920343.0' >
<HeaderFields JMSPriority='7' JMSRedelivered='false' />
<UserProperties Make='Honda' Model='Civic' Color='White'Weight='2680' />
</ExpiredJMSMessage>

If no header fields are displayed, the line for header fields is not be displayed. If no user properties are displayed, that line is not be displayed. If there are no header fields and no properties, the closing </ExpiredJMSMessage> tag is not necessary as the opening tag can be terminated with a closing bracket (/>).

For example:

<ExpiredJMSMessage JMSMessageID='ID:N<223476.1022177121567.1' />

All values are delimited with double quotes. All string values are limited to 32 characters in length. Requested fields and/or properties that do not exist are not displayed. Requested fields and/or properties that exist but have no value (a null value) are displayed as null (without single quotes). Requested fields and/or properties that are empty strings are displayed as a pair of single quotes with no space between them.

For example:

<ExpiredJMSMessage JMSMessageID='ID:N<851839.1022176920344.0' >
<UserProperties First='Any string longer than 32 char ...' Second=null Third='' />
</ExpiredJMSMessage>

Tuning Active Message Expiration

Use the Active Expiration feature to define the timeliness in which expired messages are removed from the destination to which they were sent or published. Messages are not necessarily removed from the system at their expiration time, but they are removed within a user-defined number of seconds. The smaller the window, the closer the message removal is to the actual expiration time.

Configuring a JMS Server to Actively Scan Destinations for Expired Messages

Follow these directions to define how often a JMS server will actively scan its destinations for expired messages. The default value is 30 seconds, which means the JMS server waits 30 seconds between each scan interval.

1. Follow the directions for navigating to the JMS Server: Configuration: General page of the Administration Console in "Configure general JMS server properties" in the Oracle WebLogic Server Administration Console Help.

2. In the Scan Expiration Interval field, enter the amount of time, in seconds, that you want the JMS server to pause between its cycles of scanning its destinations for expired messages to process.
To disable active scanning, enter a value of 0 seconds. Expired messages are passively removed from the system as they are discovered.

For more information about the Expiration Scan Interval attribute, see "JMS Server: Configuration: General" in the Oracle WebLogic Server Administration Console Help.

3. Click Save.

There are a number of design choices that impact performance of JMS applications. Some others include reliability, scalability, manageability, monitoring, user transactions, message driven bean support, and integration with an application server. In addition, there are WebLogic JMS extensions and features have a direct impact on performance.

For more information on designing your applications for JMS, see "Best Practices for Application Design" in Programming JMS for Oracle WebLogic Server.

Tuning Applications Using Unit-of-Order

Message Unit-of-Order is a WebLogic Server value-added feature that enables a stand-alone message producer, or a group of producers acting as one, to group messages into a single unit with respect to the processing order (a sub-ordering). This single unit is called a Unit-of-Order (or UOO) and requires that all messages from that unit be processed sequentially in the order they were created. UOO replaces the following complex design patterns:

- A dedicated consumer with a unique selector per each sub-ordering

- A new destination per sub-ordering, one consumer per destination.

See "Using Message Unit-of-Order" in Programming JMS for Oracle WebLogic Server.

Best Practices

The following sections provide best practice information when using UOO:

- Ideal for applications that have strict message ordering requirements. UOO simplifies administration and application design, and in most applications improves performance.

- Use MDB batching to:

- Speed-up processing of the messages within a single sub-ordering.

- Consume multiple messages at a time under the same transaction.
See Chapter 11, "Tuning Message-Driven Beans".

- You can configure a default UOO for the destination. Only one consumer on the destination processes messages for the default UOO at a time.

Using UOO and Distributed Destinations

To ensure strict ordering when using distributed destinations, each different UOO is pinned to a specific physical destination instance. There are two options for automatically determining the correct physical destination for a given UOO:

- Hashing – Is generally faster and the UOO setting. Hashing works by using a hash function on the UOO name to determine the physical destination. It has the following drawbacks:

- It doesn't correctly handle the administrative deleting or adding physical destinations to a distributed destination.

- If a UOO hashes to an unavailable destination, the message send fails.

- Path Service – Is a single server UOO directory service that maps the physical destination for each UOO. The Path Service is generally slower than hashing if there are many differently named UOO created per second. In this situation, each new UOO name implicitly forces a check of the path service before sending the message. If the number of UOOs created per second is limited, Path Service performance is not an issue as the UOO paths are cached throughout the cluster.

Migrating Old Applications to Use UOO

For releases prior to WebLogic Server 9.0, applications that had strict message ordering requirements were required to do the following:

- Use a single physical destination with a single consumer

- Ensure the maximum asynchronous consumer message backlog (The MessagesMaximum parameter on the connection factory) was set to a value of 1.

UOO relaxes these requirements significantly as it allows for multiple consumers and allows for a asynchronous consumer message backlog of any size. To migrate older applications to take advantage of UOO, simply configure a default UOO name on the physical destination. See "Configure connection factory unit-of-order parameters" in Oracle WebLogic Server Administration Console Help and "Ordered Redelivery of Messages" in Programming JMS for Oracle WebLogic Server.

Using One-Way Message Sends

One-way message sends can greatly improve the performance of applications that are bottle-necked by senders, but do so at the risk of introducing a lower QOS (quality-of-service). Typical message sends from a JMS producer are termed two-way sends because they include both an internal request and an internal response. When an producer application calls send(), the call generates a request that contains the application's message and then waits for a response from the JMS server to confirm its receipt of the message. This call-and-response mechanism regulates the producer, since the producer is forced to wait for the JMS server's response before the application can make another send call. Eliminating the response message eliminates this wait, and yields a one-way send. WebLogic Server supports a configurable one-way send option for non-persistent, non-transactional messaging; no application code changes are required to leverage this feature.

By enabling the One-Way Send Mode options, you allow message producers created by a user-defined connection factory to do one-way message sends, when possible. When active, the associated producers can send messages without internally waiting for a response from the target destination's host JMS server. You can choose to allow queue senders and topic publishers to do one-way sends, or to limit this capability to topic publishers only. You must also specify a One-Way Window Size to determine when a two-way message is required to regulate the producer before it can continue making additional one-way sends.

Configure One-Way Sends On a Connection Factory

You configure one-way message send parameters on a connection factory by using the Administration Console, as described in "Configure connection factory flow control" in the Oracle WebLogic Server Administration Console Help. You can also use the WebLogic Scripting Tool (WLST) or JMX via the FlowControlParamsBean MBean.

Note:

One-way message sends are disabled if your connection factory is configured with "XA Enabled". This setting disables one-way sends whether or not the sender actually uses transactions.

One-Way Send Support In a Cluster With a Single Destination

To ensure one-way send support in a cluster with a single destination, verify that the connection factory and the JMS server hosting the destination are targeted to the same WebLogic server. The connection factory must not be targeted to any other WebLogic Server instances in the cluster.

One-Way Send Support In a Cluster With Multiple Destinations

To ensure one-way send support in a cluster with multiple destinations that share the same name, special care is required to ensure the WebLogic Server instance that hosts the client connection also hosts the destination. One solution is the following:

1. Configure the cluster wide RMI load balancing algorithm to "Server Affinity".

2. Ensure that no two destinations are hosted on the same WebLogic Server instance.

3. Configure each destination to have the same local-jndi-name.

4. Configure a connection factory that is targeted to only those WebLogic Server instances that host the destinations.

5. Ensure sender clients use the JNDI names configured in Steps 3 and 4 to obtain their destination and connection factory from their JNDI context.

6. Ensure sender clients use URLs limited to only those WebLogic Server instances that host the destinations in Step 3.

This solution disables RMI-level load balancing for clustered RMI objects, which includes EJB homes and JMS connection factories. Effectively, the client will obtain a connection and destination based only on the network address used to establish the JNDI context. Load balancing can be achieved by leveraging network load balancing, which occurs for URLs that include a comma-separated list of WebLogic Server addresses, or for URLs that specify a DNS name that resolves to a round-robin set of IP addresses (as configured by a network administrator).

For more information on Server Affinity for clusters, see "Load Balancing for EJBs and RMI Objects" in Using Clusters for Oracle WebLogic Server.

When One-Way Sends Are Not Supported

This section defines when one-way sends are not supported. When one-ways are not supported, the send QOS is automatically upgraded to standard two-ways.

Different Client and Destination Hosts

One-way sends are supported when the client producer's connection host and the JMS server hosting the target destination are the same WebLogic Server instance; otherwise, the one-way mode setting will ignored and standard two-way sends will be used instead.

XA Enabled On Client's Host Connection Factory

One-way message sends are disabled if the client's host connection factory is configured with XA Enabled. This setting disables one-way sends whether or not the sender actually uses transactions.

Higher QOS Detected

When the following higher QOS features are detected, then the one-way mode setting will be ignored and standard two-way sends will be used instead:

- XA

- Transacted sessions

- Persistent messaging

- Unit-of-order

- Unit-of-work

- Distributed destinations

Destination Quota Exceeded

When the specified quota is exceeded on the targeted destination, then standard two-way sends will be used until the quota clears.

One-way messages that exceed quota are silently deleted, without immediately throwing exceptions back to the client. The client will eventually get a quota exception if the destination is still over quota at the time the next two-way send occurs. (Even in one-way mode, clients will send a two-way message every One Way Send Window Size number of messages configured on the client's connection factory.)

A workaround that helps avoid silently-deleted messages during quota conditions is to increase the value of the Blocking Send Timeout configured on the connection factory, as described in Compressing Messages. The one-way messages will not be deleted immediately, but instead will optimistically wait on the JMS server for the specified time until the quota condition clears (presumably due to messages getting consumed or by messages expiring). The client sender will not block until it sends a two-way message. For each client, no more than One Way Window Size messages will accumulate on the server waiting for quota conditions to clear.

Change In Server Security Policy

A change in the server-side security policy could prevent one-way message sends without notifying the JMS client of the change in security status.

Change In JMS Server or Destination Status

One-way sends can be disabled when a host JMS server or target destination is administratively undeployed, or when message production is paused on either the JMS server or the target destination using the "Production Pause/Resume" feature. See "Production Pause and Production Resume" in Configuring and Managing JMS for Oracle WebLogic Server.

Looking Up Logical Distributed Destination Name

One-way message sends work with distributed destinations provided the client looks up the physical distributed destination members directly rather than using the logical distributed destination's name. See "Using Distributed Destinations" in Programming JMS for Oracle WebLogic Server.

Hardware Failure

A hardware or network failure will disable one-way sends. In such cases, the JMS producer is notified by an OnException or by the next two-way message send. (Even in one-way mode, clients will send a two-way message every One Way Send Window Size number of messages configured on the client's connection factory.) The producer will be closed. The worst-case scenario is that all messages can be lost up to the last two-way message before the failure occurred.

One-Way Send QOS Guidelines

Use the following QOS-related guidelines when using the one-way send mode for typical non-persistent messaging.

- When used in conjunction with the Blocking Sends feature, then using one-way sends on a well-running system should achieve similar QOS as when using the two-way send mode.

- One-way send mode for topic publishers falls within the QOS guidelines set by the JMS Specification, but does entail a lower QOS than two-way mode (the WebLogic Server default mode).

- One-way send mode may not improve performance if JMS consumer applications are a system bottleneck, as described in "Asynchronous vs. Synchronous Consumers" in Programming JMS for Oracle WebLogic Server.

- Consider enlarging the JVM's heap size on the client and/or server to account for increased batch size (the Window) of sends. The potential memory usage is proportioned to the size of the configured Window and the number of senders.

- The sending application will not receive all quota exceptions. One-way messages that exceed quota are silently deleted, without throwing exceptions back to the sending client. See Destination Quota Exceeded for more information and a possible work around.

- Configuring one-way sends on a connection factory effectively disables any message flow control parameters configured on the connection factory.

- By default, the One-way Window Size is set to "1", which effectively disables one-way sends as every one-way message will be upgraded to a two-way send. (Even in one-way mode, clients will send a two-way message every One Way Send Window Size number of messages configured on the client's connection factory.) Therefore, you must set the one-way send window size much higher. It is recommended to try setting the window size to "300" and then adjust it according to your application requirements.

- The client application will not immediately receive network or server failure exceptions, some messages may be sent but silently deleted until the failure is detected by WebLogic Server and the producer is automatically closed. See Hardware Failure for more information.

Tuning the Messaging Performance Preference Option

Note:

This is an advanced option for fine tuning. It is normally best to explore other tuning options first.

The Messaging Performance Preference tuning option on JMS destinations enables you to control how long a destination should wait (if at all) before creating full batches of available messages for delivery to consumers. At the minimum value, batching is disabled. Tuning above the default value increases the amount of time a destination is willing to wait before batching available messages. The maximum message count of a full batch is controlled by the JMS connection factory's Messages Maximum per Session setting.

Using the Administration Console, this advanced option is available on the General Configuration page for both standalone and uniform distributed destinations (or via the DestinationBean API), as well as for JMS templates (or via the TemplateBean API).

Specifically, JMS destinations include internal algorithms that attempt to automatically optimize performance by grouping messages into batches for delivery to consumers. In response to changes in message rate and other factors, these algorithms change batch sizes and delivery times. However, it isn't possible for the algorithms to optimize performance for every messaging environment. The Messaging Performance Preference tuning option enables you to modify how these algorithms react to changes in message rate and other factors so that you can fine-tune the performance of your system.

Messaging Performance Configuration Parameters

The Message Performance Preference option includes the following configuration parameters:

Table 14-4 Message Performance Preference Values

Administration Console Value

MBean Value

Description

Do Not Batch Messages

0

Effectively disables message batching. Available messages are promptly delivered to consumers.

This is equivalent to setting the value of the connection factory's Messages Maximum per Session field to "1".

Batch Messages Without Waiting

25 (default)

Less-than-full batches are immediately delivered with available messages.

This is equivalent to the value set on the connection factory's Messages Maximum per Session field.

Low Waiting Threshold for Message Batching

50

Wait briefly before less-than-full batches are delivered with available messages. `

Medium Waiting Threshold for Message Batching

75

Possibly wait longer before less-than-full batches are delivered with available messages.

High Waiting Threshold for Message Batching

100

Possibly wait even longer before less-than-full batches are delivered with available messages.

It may take some experimentation to find out which value works best for your system. For example, if you have a queue with many concurrent message consumers, by selecting the Administration Console's Do Not Batch Messages value (or specifying "0" on the DestinationBean MBean), the queue will make every effort to promptly push messages out to its consumers as soon as they are available. Conversely, if you have a queue with only one message consumer that doesn't require fast response times, by selecting the console's High Waiting Threshold for Message Batching value (or specifying "100" on the DestinationBean MBean), then the queue will strongly attempt to only push messages to that consumer in batches, which will increase the waiting period but may improve the server's overall throughput by reducing the number of sends.

For instructions on configuring Messaging Performance Preference parameters on a standalone destinations, uniform distributed destinations, or JMS templates using the Administration Console, see the following sections in the Administration Console Online Help:

- "Configure advanced topic parameters"

- "Configure advanced queue parameters"

- "Uniform distributed topics - configure advanced parameters"

- "Uniform distributed queues - configure advanced parameters"

- "Configure advanced JMS template parameters"

For more information about these parameters, see DestinationBean and TemplateBean in the Oracle WebLogic Server MBean Reference.

Compatibility With the Asynchronous Message Pipeline

The Message Performance Preference option is compatible with asynchronous consumers using the Asynchronous Message Pipeline, and is also compatible with synchronous consumers that use the Prefetch Mode for Synchronous Consumers feature, which simulates the Asynchronous Message Pipeline. However, if the value of the Maximum Messages value is set too low, it may negate the impact of the destination's higher-level performance algorithms (e.g., Low, Medium, and High Waiting Threshold for Message Batching). For more information on the Asynchronous Message Pipeline, see "Receiving Messages" in Programming JMS for Oracle WebLogic Server.

Client-side Thread Pools

With most java client side applications, the default client thread pool size of 5 threads is sufficient. If, however, the application has a large number of asynchronous consumers, then it is often beneficial to allocate slightly more threads than asynchronous consumers. This allows more asynchronous consumers to run concurrently.

WebLogic client thread pools are configured differently than WebLogic server thread-pools, and are not self tuning. WebLogic clients have a specific thread pool that is used for handling incoming requests from the server, such as JMS MessageListener invocations. This pool can be configured via the command-line property:

-Dweblogic.ThreadPoolSize=n

where n is the number of threads

You can force a client-side thread dump to verify that this setting is taking effect.

Best Practices for JMS .NET Client Applications

The following is a short list of performance related best practices to use when creating a JMS .NET client application:

- Always register a connection exception listener using an IConnection if the application needs to take action when an idle connection fails.

- Have multiple .NET client threads share a single context to ensure that they use a single socket.

- Cache and reuse frequently accessed JMS resources, such as contexts, connections, sessions, producers, destinations, and connection factories. Creating and closing these resources consumes significant CPU and network bandwidth.

- Use DNS aliases or comma separated addresses for load balancing JMS .NET clients across multiple JMS .NET client host servers in a cluster.

For more information on best practices and other programming considerations for JMS .NET client applications, see "Programming Considerations" in Use the WebLogic JMS Client for Microsoft .NET.

15 Tuning WebLogic JMS Store-and-Forward

This chapter provides information on how to get the best performance from Store-and-Forward (SAF) applications. For WebLogic Server releases 9.0 and higher, JMS provides advanced store-and-forward capability for high-performance message forwarding from a local server instance to a remote JMS destination. See "Understanding the Store-and-Forward Service" in Configuring and Managing Store-and-Forward for Oracle WebLogic Server.

- Best Practices

- Tuning Tips

Best Practices

- Avoid using SAF if remote destinations are already highly available. JMS clients can send directly to remote destinations. Use SAF in situations where remote destinations are not highly available, such as an unreliable network or different maintenance schedules.

- Use the better performing JMS SAF feature instead of using a Messaging Bridge when forwarding messages to remote destinations. In general, a JMS SAF agent is significantly faster than a Messaging Bridge. One exception is a configuration when sending messages in a non-persistent exactly-once mode.

Note:

A Messaging Bridge is still required to store-and-forward messages to foreign destinations and destinations from releases prior to WebLogic 9.0.

- Configure separate SAF Agents for JMS SAF and Web Services Reliable Messaging Agents (WS-RM) to simplify administration and tuning.

- Sharing the same WebLogic Store between subsystems provides increased performance for subsystems requiring persistence. For example, transactions that include SAF and JMS operations, transactions that include multiple SAF destinations, and transactions that include SAF and EJBs. See Tuning the WebLogic Persistent Store.

Tuning Tips

- Target imported destinations to multiple SAF agents to load balance message sends among available SAF agents.

- Increase the JMS SAF Window Size for applications that handle small messages. By default, a JMS SAF agent forwards messages in batches that contain up to 10 messages. For small messages size, it is possible to double or triple performance by increasing the number of messages in each batch to be forwarded. A more appropriate initial value for Window Size for small messages is 100. You can then optimize this value for your environment.
Changing the Window Size for applications handling large message sizes is not likely to increase performance and is not recommended. Window Size also tunes WS-RM SAF behavior, so it may not be appropriate to tune this parameter for SAF Agents of type Both.

Note:

For a distributed queue, WindowSize is ignored and the batch size is set internally at 1 message.

- Increase the JMS SAF Window Interval. By default, a JMS SAF agent has a Window Interval value of 0 which forwards messages as soon as they arrive. This can lower performance as it can make the effective Window size much smaller than the configured value. A more appropriate initial value for Window Interval value is 500 milliseconds. You can then optimize this value for your environment. In this context, small messages are less than a few K, while large messages are on the order of tens of K.
Changing the Window Interval improves performance only in cases where the forwarder is already able to forward messages as fast as they arrive. In this case, instead of immediately forwarding newly arrived messages, the forwarder pauses to accumulate more messages and forward them as a batch. The resulting larger batch size improves forwarding throughput and reduces overall system disk and CPU usage at the expense of increasing latency.

Note:

For a distributed queue, Window Interval is ignored.

- Set the Non-Persistent QOS value to At-Least-Once for imported destinations if your application can tolerate duplicate messages.

16 Tuning WebLogic Message Bridge

This chapter provides information on various methods to improve message bridge performance.

- Best Practices

- Changing the Batch Size

- Changing the Batch Interval

- Changing the Quality of Service

- Using Multiple Bridge Instances

- Changing the Thread Pool Size

- Avoiding Durable Subscriptions

- Co-locating Bridges with Their Source or Target Destination

- Changing the Asynchronous Mode Enabled Attribute

Best Practices

- Avoid using a Messaging Bridge if remote destinations are already highly available. JMS clients can send directly to remote destinations. Use messaging bridge in situations where remote destinations are not highly available, such as an unreliable network or different maintenance schedules.

- Use the better performing JMS SAF feature instead of using a Messaging Bridge when forwarding messages to remote destinations. In general, a JMS SAF agent is significantly faster than a Messaging Bridge. One exception is a configuration when sending messages in a non-persistent exactly-once mode.

Note:

A Messaging Bridge is still required to store-and-forward messages to foreign destinations and destinations from releases prior to WebLogic 9.0.

Changing the Batch Size

When the Asynchronous Mode Enabled attribute is set to false and the quality of service is Exactly-once, the Batch Size attribute can be used to reduce the number of transaction commits by increasing the number of messages per transaction (batch). The best batch size for a bridge instance depends on the combination of JMS providers used, the hardware, operating system, and other factors in the application environment. See "Configure transaction properties" in Oracle WebLogic Server Administration Console Help.

Changing the Batch Interval

When the Asynchronous Mode Enabled attribute is set to false and the quality of service is Exactly-once, the BatchInterval attribute is used to adjust the amount of time the bridge waits for each batch to fill before forwarding batched messages. The best batch interval for a bridge instance depends on the combination of JMS providers used, the hardware, operating system, and other factors in the application environment. For example, if the queue is not very busy, the bridge may frequently stop forwarding in order to wait batches to fill, indicating the need to reduce the value of the BatchInterval attribute. See "Configure transaction properties" in Oracle WebLogic Server Administration Console Help.

Changing the Quality of Service

An Exactly-once quality of service may perform significantly better or worse than At-most-once and Duplicate-okay.

When the Exactly-once quality of service is used, the bridge must undergo a two-phase commit with both JMS servers in order to ensure the transaction semantics and this operation can be very expensive. However, unlike the other qualities of service, the bridge can batch multiple operations together using Exactly-once service.

You may need to experiment with this parameter to get the best possible performance. For example, if the queue is not very busy or if non-persistent messages are used, Exactly-once batching may be of little benefit. See "Configure messaging bridge instances" in Oracle WebLogic Server Administration Console Help.

Using Multiple Bridge Instances

If message ordering is not required, consider deploying multiple bridges.

Multiple instances of the bridge may be deployed using the same destinations. When this is done, each instance of the bridge runs in parallel and message throughput may improve. If multiple bridge instances are used, messages will not be forwarded in the same order they had in the source destination. See "Create messaging bridge instances" in Oracle WebLogic Server Administration Console Help.

Consider the following factors when deciding whether to use multiple bridges:

- Some JMS products do not seem to benefit much from using multiple bridges

- WebLogic JMS messaging performance typically improves significantly, especially when handling persistent messages.

- If the CPU or disk storage is already saturated, increasing the number of bridge instances may decrease throughput.

Changing the Thread Pool Size

A general bridge configuration rule is to provide a thread for each bridge instance targeted to a server instance. Use one of the following options to ensure that an adequate number of threads is available for your environment:

- Use the common thread pool—A server instance changes its thread pool size automatically to maximize throughput, including compensating for the number of bridge instances configured. See "Understanding How WebLogic Server Uses Thread Pools" in Configuring Server Environments for Oracle WebLogic Server.

- Configure a work manager for the weblogic.jms.MessagingBridge class. See "Understanding Work Managers" in Designing and Configuring WebLogic Server Environments.

- Use the Administration console to set the Thread Pool Size property in the Messaging Bridge Configuration section on the Configuration: Services page for a server instance. To avoid competing with the default execute thread pool in the server, messaging bridges share a separate thread pool. This thread pool is used only in synchronous mode (Asynchronous Mode Enabled is not set). In asynchronous mode the bridge runs in a thread created by the JMS provider for the source destination. Deprecated in WebLogic Server 9.0.

Avoiding Durable Subscriptions

If the bridge is listening on a topic and it is acceptable that messages are lost when the bridge is not forwarding messages, disable the Durability Enabled flag to ensure undeliverable messages do not accumulate in the source server's store. Disabling the flag also makes the messages non-persistent. See "Configure messaging bridge instances" in Oracle WebLogic Server Administration Console Help.

Co-locating Bridges with Their Source or Target Destination

If a messaging bridge source or target is a WebLogic destination, deploy the bridge to the same WebLogic server as the destination. Targeting a messaging bridge with one of its destinations eliminates associated network and serialization overhead. Such overhead can be significant in high-throughput applications, particularly if the messages are non-persistent.

Changing the Asynchronous Mode Enabled Attribute

The Asynchronous Mode Enabled attribute determines whether the messaging bridge receives messages asynchronously using the JMS MessageListener interface at http://docs.oracle.com/javaee/5/api/javax/jms/MessageListener.html, or whether the bridge receives messages using the synchronous JMS APIs. In most situations, the Asynchronous Enabled attributes value is dependent on the QOS required for the application environment as shown in Table 16-1:

Table 16-1 Asynchronous Mode Enabled Values for QOS Level

QOS

Asynchronous Mode Enabled Attribute value

Exactly-onceFoot 1

false

At-least-once

true

At-most-once

true

Footnote 1 If the source destination is a non-WebLogic JMS provider and the QOS is Exactly-once, then the Asynchronous Mode Enabled attribute is disabled and the messages are processed in synchronous mode.

See "Configure messaging bridge instances" in Oracle WebLogic Server Administration Console Help.

A quality of service of Exactly-once has a significant effect on bridge performance. The bridge starts a new transaction for each message and performs a two-phase commit across both JMS servers involved in the transaction. Since the two-phase commit is usually the most expensive part of the bridge transaction, as the number of messages being processed increases, the bridge performance tends to decrease.

17 Tuning Resource Adapters

This chapter describes best practices for tuning resource adapters.

- Classloading Optimizations for Resource Adapters

- Connection Optimizations

- Thread Management

- InteractionSpec Interface

Classloading Optimizations for Resource Adapters

You can package resource adapter classes in one or more JAR files, and then place the JAR files in the RAR file. These are called nested JARs. When you nest JAR files in the RAR file, and classes need to be loaded by the classloader, the JARs within the RAR file must be opened and closed and iterated through for each class that must be loaded.

If there are very few JARs in the RAR file and if the JARs are relatively small in size, there will be no significant performance impact. On the other hand, if there are many JARs and the JARs are large in size, the performance impact can be great.

To avoid such performance issues, you can either:

1. Deploy the resource adapter in an exploded format. This eliminates the nesting of JARs and hence reduces the performance hit involved in looking for classes.

2. If deploying the resource adapter in exploded format is not an option, the JARs can be exploded within the RAR file. This also eliminates the nesting of JARs and thus improves the performance of classloading significantly.

Connection Optimizations

Oracle recommends that resource adapters implement the optional enhancements described in sections 7.14.2 and 7.14.2 of the J2CA 1.5 Specification at http://java.sun.com/j2ee/connector/download.html. Implementing these interfaces allows WebLogic Server to provide several features that will not be available without them.

Lazy Connection Association, as described in section 7.14.1, allows the server to automatically clean up unused connections and prevent applications from hogging resources. Lazy Transaction Enlistment, as described in 7.14.2, allows applications to start a transaction after a connection is already opened.

Thread Management

Resource adapter implementations should use the WorkManager (as described in Chapter 10, "Work Management" in the J2CA 1.5 Specification at http://java.sun.com/j2ee/connector/download.html) to launch operations that need to run in a new thread, rather than creating new threads directly. This allows WebLogic Server to manage and monitor these threads.

InteractionSpec Interface

WebLogic Server supports the Common Client Interface (CCI) for EIS access, as defined in Chapter 15, "Common Client Interface" in the J 2CA 1.5 Specification at http://java.sun.com/j2ee/connector/. The CCI defines a standard client API for application components that enables application components and EAI frameworks to drive interactions across heterogeneous EISes.

As a best practice, you should not store the InteractionSpec class that the CCI resource adapter is required to implement in the RAR file. Instead, you should package it in a separate JAR file outside of the RAR file, so that the client can access it without having to put the InteractionSpec interface class in the generic CLASSPATH.

With respect to the InteractionSpec interface, it is important to remember that when all application components (EJBs, resource adapters, Web applications) are packaged in an EAR file, all common classes can be placed in the APP-INF/lib directory. This is the easiest possible scenario.

This is not the case for standalone resource adapters (packaged as RAR files). If the interface is serializable (as is the case with InteractionSpec), then both the client and the resource adapter need access to the InteractionSpec interface as well as the implementation classes. However, if the interface extends java.io.Remote, then the client only needs access to the interface class.

18 Tuning Web Applications

This chapter describes Oracle best practices for tuning Web applications and managing sessions.

- Best Practices

- Session Management

- Pub-Sub Tuning Guidelines

Best Practices

- Disable Page Checks

- Use Custom JSP Tags

- Precompile JSPs

- Disable Access Logging

- Use HTML Template Compression

- Use Service Level Agreements

- Related Reading

Disable Page Checks

You can improve performance by disabling servlet and JDP page checks. Set each of the following parameters to -1:

- pageCheckSeconds

- servlet-reload-check-secs

- servlet Reload Check

These are default values for production mode.

Use Custom JSP Tags

Oracle provides three specialized JSP tags that you can use in your JSP pages: cache, repeat, and process. These tags are packaged in a tag library jar file called weblogic-tags.jar. This jar file contains classes for the tags and a tag library descriptor (TLD). To use these tags, you copy this jar file to the Web application that contains your JSPs and reference the tag library in your JSP. See "Using Custom WebLogic JSP Tags (cache, process, repeat)" in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server.

Precompile JSPs

You can configure WebLogic Server to precompile your JSPs when a Web Application is deployed or re-deployed or when WebLogic Server starts up by setting the precompile parameter to true in the jsp-descriptor element of the weblogic.xml deployment descriptor. To avoid recompiling your JSPs each time the server restarts and when you target additional servers, precompile them using weblogic.jspc and place them in the WEB-INF/classes folder and archive them in a .war file. Keeping your source files in a separate directory from the archived .war file eliminates the possibility of errors caused by a JSP having a dependency on one of the class files. For a complete explanation on how to avoid JSP recompilation, see "Avoiding Unnecessary JSP Compilation" at http://www.oracle.com/technology/pub/articles/dev2arch/2005/01/jsp_reloaded.html.

Disable Access Logging

Setting the access-logging-disabled element can eliminate access logging of the underlying Web application, which can improve server throughput by reducing the logging overhead. See container-descriptor in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server.

Use HTML Template Compression

Using the compress-html-template element compresses the HTML in the JSP template blocks which can improve runtime performance. If the JSP's HTML template block contains the <pre> HTML tag, do not enable this feature.

See jsp-descriptor in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server.

Use Service Level Agreements

You should assign servlets and JSPs to work managers based on the service level agreements required by your applications. See Thread Management.

Related Reading

- "Servlet Best Practices" in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server.

- "Servlet and JSP Performance Tuning" at http://www.javaworld.com/javaworld/jw-06-2004/jw-0628-performance_p.html, by Rahul Chaudhary, JavaWorld, June 2004.

Session Management

As a general rule, you should optimize your application so that it does as little work as possible when handling session persistence and sessions. The following sections provide information on how to design a session management strategy that suits your environment and application:

- Managing Session Persistence

- Minimizing Sessions

- Aggregating Session Data

Managing Session Persistence

WebLogic Server offers many session persistence mechanisms that cater to the differing requirements of your application, including Async-replicated and Async-JDBC modes. The session persistence mechanisms are configurable at the Web application layer. Which session management strategy you choose for your application depends on real-world factors like HTTP session size, session life cycle, reliability, and session failover requirements. For example, a Web application with no failover requirements could be maintained as a single memory-based session; whereas, a Web application with session fail-over requirements could be maintained as replicated sessions or JDBC-based sessions, based on their life cycle and object size.

In terms of pure performance, replicated session persistence is a better overall choice when compared to JDBC-based persistence for session state. However, replicated-based session persistence requires the use of WebLogic clustering, so it isn't an option in a single-server environment.

On the other hand, an environment using JDBC-based persistence does not require the use of WebLogic clusters and can maintain the session state for longer periods of time in the database. One way to improve JDBC-based session persistence is to optimize your code so that it has as high a granularity for session state persistence as possible. Other factors that can improve the overall performance of JDBC-based session persistence are: the choice of database, proper database server configuration, JDBC driver, and the JDBC connection pool configuration.

For more information on managing session persistence, see:

- "Configuring Session Persistence" in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server

- "HTTP Session State Replication" in Using Clusters for Oracle WebLogic Server

- "Using a Database for Persistent Storage (JDBC Persistence)" in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server

Minimizing Sessions

Configuring how WebLogic Server manages sessions is a key part of tuning your application for best performance. Consider the following:

- Use of sessions involves a scalability trade-off.

- Use sessions sparingly. In other words, use sessions only for state that cannot realistically be kept on the client or if URL rewriting support is required. For example, keep simple bits of state, such as a user's name, directly in cookies. You can also write a wrapper class to "get" and "set" these cookies, in order to simplify the work of servlet developers working on the same project.

- Keep frequently used values in local variables.

For more information, see "Setting Up Session Management" in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server.

Aggregating Session Data

This section provides best practices on how to aggregate session data. WebLogic Server tracks and replicates changes in the session by attribute so you should:

- Aggregate session data that changes in tandem into a single session attribute.

- Aggregate session data that changes frequently and read-only session data into separate session attributes

For example: If you use a a single large attribute that contains all the session data and only 10% of that data changes, the entire attribute has to be replicated. This causes unnecessary serialization/deserialization and network overhead. You should move the 10% of the session data that changes into a separate attribute.

Pub-Sub Tuning Guidelines

The following section provides general tuning guidelines for a pub-sub server:

- Increase file descriptors to cater for a large number of long-living connections, especially for applications with thousands of clients.

- Tune logging level for WebLogic Server.

- Disable Access Logging.

- Tune JVM options. Suggested options: -Xms1536m -Xmx1536m -Xns512m -XXtlaSize:min=128k,preferred=256k

- Increase the maximum message. If your application publishes messages under high volumes, consider setting the value to <max-message-size>10000000</max-message-size>.

19 Tuning Web Services

This chapter describes Oracle best practices for designing, developing, and deploying WebLogic Web Services applications and application resources.

- Web Services Best Practices

- Tuning Web Service Reliable Messaging Agents

- Tuning Heavily Loaded Systems to Improve Web Service Performance

Web Services Best Practices

Design and architectural decisions have a strong impact on runtime performance and scalability of Web Service applications. Here are few key recommendations to achieve best performance.

- Design Web Service applications for course-grained service with moderate size payloads.

- Choose correct service-style & encoding for your Web service application.

- Control serializer overheads and namespaces declarations to achieve better performance.

- Use MTOM/XOP or Fast Infoset to optimizing the format of a SOAP message.

- Carefully design SOAP attachments and security implementations for minimum performance overheads.

- Consider using an asynchronous messaging model for applications with:

- Slow and unreliable transport.

- Complex and long-running process.

- For transactional Service Oriented Architectures (SOA) consider using the Last Logging Resource transaction optimization (LLR) to improve performance. See Tuning Transactions.

- Use replication and caching of data and schema definitions to improve performance by minimizing network overhead.

- Consider any XML compression technique only when XML compression/decompression overheads are less than network overheads involved.

- Applications that are heavy users of XML functionality (parsers) may encounter performance issues or run out of file descriptors. This may occur because XML parser instances are bootstrapped by doing a lookup in the jaxp.properties file (JAXP API). Oracle recommends setting the properties on the command line to avoid unnecessary file operations at runtime and improve performance and resource usage.

- Follow "JWS Programming Best Practices" in Getting Started With JAX-WS Web Services for Oracle WebLogic Server.

- Follow best practice and tuning recommendations for all underlying components, such as Tuning WebLogic Server EJBs, Tuning Web Applications, Tuning Data Sources, and Tuning WebLogic JMS.

Tuning Web Service Reliable Messaging Agents

Web Service Reliable Messaging provides advanced store-and-forward capability for high-performance message forwarding from a local server instance to a remote destination. See "Understanding the Store-and-Forward Service" in Configuring and Managing Store-and-Forward for Oracle WebLogic Server. The following section provides information on how to get the best performance from Store-and-Forward (SAF) applications:

- Configure separate SAF Agents for JMS SAF and Web Services Reliable Messaging Agents to simplify administration and tuning.

- Sharing the same WebLogic Store between subsystems provides increased performance for subsystems requiring persistence. For example, transactions that include SAF and JMS operations, transactions that include multiple SAF destinations, and transactions that include SAF and EJBs. See Tuning the WebLogic Persistent Store.

- Consider increasing the WindowSize parameter on the remote SAF agent. For small messages of less than 1K, tuning WindowSize as high as 300 can improve throughput.

Note:

WindowSize also tunes JMS SAF behavior, so it may not be appropriate to tune this parameter for SAF agents of type both.

- Ensure that retry delay is not set too low. This may cause the system to make unnecessary delivery attempts.

Tuning Heavily Loaded Systems to Improve Web Service Performance

The asynchronous request-response, reliable messaging, and buffering features are all pre-tuned for minimum system resource usage to support a small number of clients (under 10). If you plan on supporting a larger number of clients or high message volumes, you should adjust the tuning parameters to accommodate the additional load, as described in the following sections:

- Setting the Work Manager Thread Pool Minimum Size Constraint

- Setting the Buffering Sessions

- Releasing Asynchronous Resources

Setting the Work Manager Thread Pool Minimum Size Constraint

Define a Work Manager and set the thread pool minimum size constraint (min-threads-constraint) to a value that is at least as large as the expected number of concurrent requests or responses into the service.

For example, if a Web service client issues 20 requests in rapid succession, the recommended thread pool minimum size constraint value would be 20 for the application hosting the client. If the configured constraint value is too small, performance can be severely degraded as incoming work waits for a free processing thread.

For more information about the thread pool minimum size constraint, see "Constraints" in Configuring Server Environments for Oracle WebLogic Server.

Setting the Buffering Sessions

The reliable messaging and buffering features use JMS queue sessions to send messages to the reliability/buffer queues. By default, WebLogic Server allocates 10 sessions for buffering which enables 10 clients to enqueue messages simultaneously onto the reliability/buffer queue.

For asynchronous request-response, the request and response portion of the communication exchange count separately, as two clients. In this case, the default pool of sessions can support five simultaneous asynchronous request-response clients. To accommodate the number of concurrent clients you expect in your application, set the following parameter to twice the number of expected client threads:

-Dweblogic.wsee.buffer.QueueSessionPoolSize=size

Releasing Asynchronous Resources

When using the asynchronous request-response feature, WebLogic Server persistently stores information about the request until the asynchronous response is returned to the client. These resources remain in the persistent store until they are released by a background thread, called the store cleaner.

Often, these resources can be released sooner. Executing the store cleaner more frequently can help to reduce the size of the persistent store and minimize the time required to clean it.

By default, the store cleaner runs every two minutes (120000 ms). Oracle recommends that you set the store cleaner interval to one minute (60000 ms) using the following Java system property:

-Dweblogic.wsee.StateCleanInterval=60000

20 Tuning WebLogic Tuxedo Connector

This chapter provides information on how to get the best performance from WebLogic Tuxedo Connector (WTC) applications. The WebLogic Tuxedo Connector (WTC) provides interoperability between WebLogic Server applications and Tuxedo services. WTC allows WebLogic Server clients to invoke Tuxedo services and Tuxedo clients to invoke WebLogic Server Enterprise Java Beans (EJBs) in response to a service request. See "WebLogic Tuxedo Connector" in Information Roadmap for Oracle WebLogic Server .

- Configuration Guidelines

- Best Practices

Configuration Guidelines

Use the following guidelines when configuring WebLogic Tuxedo Connector:

- You may have more than one WTC Service in your configuration.

- You can only target one WTC Service to a server instance.

- WTC does not support connection pooling. WTC multiplexes requests though a single physical connection.

- Configuration changes implemented as follows:

- Changing the session/connection configuration (local APs, remote APs, Passwords, and Resources) before a connection/session is established. The changes are accepted and are implemented in the new session/connection.

- Changing the session/connection configuration (local APs, remote APs, Passwords, and Resources) after a connection/session is established.The changes accepted but are not implemented in the existing connection/session until the connection is disconnected and reconnected. See "Assign a WTC Service to a Server" in Oracle WebLogic Server Administration Console Help.

- Changing the Imported and Exported services configuration. The changes are accepted and are implemented in the next inbound or outbound request. Oracle does not recommend this practice as it can leave in-flight requests in an unknown state.

- Changing the tBridge configuration. Any change in a deployed WTC service causes an exception. You must untarget the WTC service before making any tBridge configuration changes. After untargeting and making configuration changes, you must target the WTC service to implement the changes.

Best Practices

The following section provides best practices when using WTC:

- When configuring the connection policy, use ON_STARTUP and INCOMING_ONLY. ON_STARTUP and INCOMING_ONLY always paired. For example: If a WTC remote access point is configured with ON_STARTUP, the DM_TDOMAIN section of the Tuxedo domain configuration must be configured with the remote access point as INCOMING_ONLY. In this case, WTC always acts as the session initiator. See "Configuring the Connections Between Access Points" in the WebLogic Tuxedo Connector Administration Guide for Oracle WebLogic Server.

- Avoid using connection policy ON_DEMAND. The preferred connection policy is ON_STARTUP and INCOMING_ONLY. This reduces the chance of service request failure due to the routing semantics of ON_DEMAND. See "Configuring the Connections Between Access Points" in the WebLogic Tuxedo Connector Administration Guide for Oracle WebLogic Server.

- Consider using the following WTC features: Link Level Failover, Service Level failover and load balancing when designing your application. See "Configuring Failover and Failback" in the WebLogic Tuxedo Connector Administration Guide for Oracle WebLogic Server.

- Consider using WebLogic Server clusters to provide additional load balancing and failover. To use WTC in a WebLogic Server cluster:

- Configure a WTC instance on all the nodes of the WebLogic Server cluster.

- Each WTC instance in each cluster node must have the same configuration.

See "How to Manage WebLogic Tuxedo Connector in a Clustered Environment" in the WebLogic Tuxedo Connector Administration Guide for Oracle WebLogic Server.

- If your WTC to Tuxedo connection uses the internet, use the following security settings:

- Set the value of Security to DM_PW. See "Authentication of Remote Access Points" in the WebLogic Tuxedo Connector Administration Guide for Oracle WebLogic Server.

- Enable Link-level encryption and set the min-encrypt-bits parameter to 40 and the max-encrypt-bits to 128. See "Link-Level Encryption" in the WebLogic Tuxedo Connector Administration Guide for Oracle WebLogic Server.

- Your application logic should provide mechanisms to manage and interpret error conditions in your applications.

- See "Application Error Management" in the WebLogic Tuxedo Connector Programmer’s Guide for Oracle WebLogic Server.

- See "System Level Debug Settings" in the WebLogic Tuxedo Connector Administration Guide for Oracle WebLogic Server.

- Avoid using embedded TypedFML32 buffers inside TypedFML32 buffers. See "Using FML with WebLogic Tuxedo Connector" in the WebLogic Tuxedo Connector Programmer’s Guide for Oracle WebLogic Server.

- If your application handles heavy loads, consider configuring more remote Tuxedo access points and let WTC load balance the work load among the access points. See "Configuring Failover and Failback" in the WebLogic Tuxedo Connector Administration Guide for Oracle WebLogic Server.

- When using transactional applications, try to make the remote services involved in the same transaction available from the same remote access point. See "WebLogic Tuxedo Connector JATMI Transactions" in the WebLogic Tuxedo Connector Programmer’s Guide for Oracle WebLogic Server.

- The number of client threads available when dispatching services from the gateway may limit the number of concurrent services running. There is no WebLogic Tuxedo Connector attribute to increase the number of available threads. Use a reasonable thread model when invoking service. See Thread Management and "Using Work Managers to Optimize Scheduled Work" in Configuring Server Environments for Oracle WebLogic Server.

- WebLogic Server Releases 9.2 and higher provide improved routing algorithms which enhance transaction performance. Specifically, performance is improved when there are more than one Tuxedo service requests involved in a 2 phase commit (2PC) transaction. If your application does only single service request to the Tuxedo domain, you can disable this feature by setting the following WebLogic Server command line parameter:

-Dweblogic.wtc.xaAffinity=false

- Call the constructor TypedFML32 using the maximum number of objects in the buffer. Even if the maximum number is difficult to predict, providing a reasonable number improves performance. You approximate the maximum number by multiplying the number of fields by 1.33.

Note:

This performance tip does not apply to TypedFML buffer type.

For example:

If there are 50 fields in a TypedFML32 buffer type then the maximum number is 63. Calling the constructor TypedFML32(63, 50) performs better than TypedFML32().

If there are 50 fields in a TypedFML32 buffer type and each can have maximum 10 occurrences, then call the constructor TypedFML32(625, 50) will give better performance than TypedFML32()

- When configuring Tuxedo applications that act as servers interoperating with WTC clients, take into account of parallelism that may be achieved by carefully configuring different servers on different Tuxedo machines.

- Be aware of the possibility of database access deadlock in Tuxedo applications. You can avoid deadlock through careful Tuxedo application configuration.

- If your are using WTC load balancing or service level failover, Oracle recommends that you do not disable WTC transaction affinity.

- For load balancing outbound requests, configure the imported service with multiple entries using a different key. The imported service uses composite key to determine each record's uniqueness. The composite key is compose of "the service name + the local access point + the primary route in the remote access point list".
The following is an example of how to correctly configure load balancing requests for service1 between TDomainSession(WDOM1,TUXDOM1) and TDomainSession(WDOM1,TUXDOM2:

Table 20-1 Example of Correctly Configured Load Balancing

ResourceName

LocalAccessPoint

RemoteAccessPointList

RemoteName

service1

WDOM1

TUXDOM1

TOLOWER

service1

WDOM1

TUXDOM2

TOLOWER2

The following is an example an incorrectly configured load balancing requests. The following configuration results in the same composite key for service1:

Table 20-2 Example of Incorrectly Configured Load Balancing

ResourceName

LocalAccessPoint

RemoteAccessPointList

RemoteName

service1

WDOM1

TUXDOM1

TOLOWER

service1

WDOM1

TUXDOM1

TOLOWER

A Using the WebLogic 8.1 Thread Pool Model

This chapter describes how to use and tune WebLogic 8.1 thread pools. If you have been using execute queues to improve performance prior to this release, you may continue to use them after you upgrade your application domains to WebLogic Server 10.x.

Oracle recommends migrating from execute queues to using the self-tuning execute queue with work managers. See "Using Work Managers to Optimize Scheduled Work" in Configuring Server Environments for Oracle WebLogic Server.

- How to Enable the WebLogic 8.1 Thread Pool Model

- Tuning the Default Execute Queue

- Using Execute Queues to Control Thread Usage

- Monitoring Execute Threads

- Allocating Execute Threads to Act as Socket Readers

- Tuning the Stuck Thread Detection Behavior

How to Enable the WebLogic 8.1 Thread Pool Model

Oracle provides a flag that enables you to disable the self-tuning execute pool and provide backward compatibility for upgraded applications to continue to use user-defined execute queues.

To use user-defined execute queues in a WebLogic Server 10.x domain, you need to include the use81-style-execute-queues sub-element of the server element in the config.xml file and reboot the server.

1. If you have not already done so, stop the WebLogic Server instance.

2. Edit the config.xml file, setting the use81-style-execute-queues element to true.

3. Reboot the server instance.

4. Explicitly create the weblogic.kernel.Default execute queue from the Administration Console.

5. Reboot the server instance.

The following example code allows an instance of myserver to use execute queues:

Example A-1 Using the use81-style-execute-queues Element

.
.
.
<server>
<name>myserver</name>
<ssl>
<name>myserver</name>
<enabled>true</enabled>
<listen-port>7002</listen-port>
</ssl>
<use81-style-execute-queues>true</use81-style-execute-queues>
<listen-address/>
</server>
.
.
.

Configured work managers are converted to execute queues at runtime by the server instance.

Tuning the Default Execute Queue

The value of the ThreadCount attribute of an ExecuteQueue element in the config.xml file equals the number of simultaneous operations that can be performed by applications that use the execute queue. As work enters an instance of WebLogic Server, it is placed in an execute queue. This work is then assigned to a thread that does the work on it. Threads consume resources, so handle this attribute with care—you can degrade performance by increasing the value unnecessarily. WebLogic Server uses different default values for the thread count of the default execute queue depending on the startup mode of the server instance. See "Specify a startup mode" in Oracle WebLogic Server Administration Console Help.

Table A-1 Default Thread Count for Startup Modes

Server Mode . . .

Default Thread Count . . .

Development

15 threads

Production

25 threads

Unless you configure additional execute queues, and assign applications to them, the server instance assigns requests to the default execute queue.

Note:

If native performance packs are not being used for your platform, you may need to tune the default number of execute queue threads and the percentage of threads that act as socket readers to achieve optimal performance. For more information, see Allocating Execute Threads to Act as Socket Readers.

Should You Modify the Default Thread Count?

Adding more threads to the default execute queue does not necessarily imply that you can process more work. Even if you add more threads, you are still limited by the power of your processor. You can degrade performance by increasing the value of the ThreadCount attribute unnecessarily. A high execute thread count causes more memory to be used and may increases context switching, which can degrade performance.

The value of the ThreadCount attribute depends very much on the type of work your application does. For example, if your client application is thin and does a lot of its work through remote invocation, that client application will spend more time connected — and thus will require a higher thread count — than a client application that does a lot of client-side processing.

If you do not need to use more than 15 threads (the development default) or 25 threads (the production default) for your work, do not change the value of this attribute. As a general rule, if your application makes database calls that take a long time to return, you will need more execute threads than an application that makes calls that are short and turn over very rapidly. For the latter case, using a smaller number of execute threads could improve performance.

To determine the ideal thread count for an execute queue, monitor the queue's throughput while all applications in the queue are operating at maximum load. Increase the number of threads in the queue and repeat the load test until you reach the optimal throughput for the queue. (At some point, increasing the number of threads will lead to enough context switching that the throughput for the queue begins to decrease.)

Note:

The WebLogic Server Administration Console displays the cumulative throughput for all of a server's execute queues. To access this throughput value, follow steps 1-6 in Using Execute Queues to Control Thread Usage.

Table A-2 shows default scenarios for adjusting available threads in relation to the number of CPUs available in the WebLogic Server domain. These scenarios also assume that WebLogic Server is running under maximum load, and that all thread requests are satisfied by using the default execute queue. If you configure additional execute queues and assign applications to specific queues, monitor results on a pool-by-pool basis.

Table A-2 Scenarios for Modifying the Default Thread Count

When...

And you see...

Do This:

Thread Count < number of CPUs

CPUs are under utilized, but there is work that could be done.

Increase the thread count.

Thread Count = number of CPUs

CPUs are under utilized, but there is work that could be done.

Increase the thread count.

Thread Count > number of CPUs (by a moderate number of threads)

CPUs have high utilization, with a moderate amount of context switching.

Tune the moderate number of threads and compare performance results.

Thread Count > number of CPUs (by a large number of threads)

Too much context switching.

Reduce the number of threads.

Using Execute Queues to Control Thread Usage

You can fine-tune an application's access to execute threads (and thereby optimize or throttle its performance) by using user-defined execute queues in WebLogic Server. However, keep in mind that unused threads represent significant wasted resources in a WebLogic Server system. You may find that available threads in configured execute queues go unused, while tasks in other queues sit idle waiting for threads to become available. In such a situation, the division of threads into multiple queues may yield poorer overall performance than having a single, default execute queue.

Default WebLogic Server installations are configured with a default execute queue which is used by all applications running on the server instance. You may want to configure additional queues to:

- Optimize the performance of critical applications. For example, you can assign a single, mission-critical application to a particular execute queue, guaranteeing a fixed number of execute threads. During peak server loads, nonessential applications may compete for threads in the default execute queue, but the mission-critical application has access to the same number of threads at all times.

- Throttle the performance of nonessential applications. For an application that can potentially consume large amounts of memory, assigning it to a dedicated execute queue effectively limits the amount of memory it can consume. Although the application can potentially use all threads available in its assigned execute queue, it cannot affect thread usage in any other queue.

- Remedy deadlocked thread usage. With certain application designs, deadlocks can occur when all execute threads are currently utilized. For example, consider a servlet that reads messages from a designated JMS queue. If all execute threads in a server are used to process the servlet requests, then no threads are available to deliver messages from the JMS queue. A deadlock condition exists, and no work can progress. Assigning the servlet to a separate execute queue avoids potential deadlocks, because the servlet and JMS queue do not compete for thread resources.

Be sure to monitor each execute queue to ensure proper thread usage in the system as a whole. See Should You Modify the Default Thread Count? for general information about optimizing the number of threads.

Creating Execute Queues

An execute queue represents a named collection of execute threads that are available to one or more designated servlets, JSPs, EJBs, or RMI objects.

To configure a new execute queue using the Administration Console:

1. If you have not already done so, in the Change Center of the Administration Console, click Lock & Edit.

2. In the left pane of the console, expand Environment > Servers.

3. On the Summary of Servers page, select the server instance for which you will configure an execute queue.

4. Select the Configuration > Queues tab and click New.

5. Name the execute queue and click OK.

6. On the User-Defined Execute Queues page, select the execute queue you just created.

7. On the execute queue Configuration tab, modify the following attributes or accept the system defaults:
Queue Length—Always leave the Queue Length at the default value of 65536 entries. The Queue Length specifies the maximum number of simultaneous requests that the server can hold in the queue. The default of 65536 requests represents a very large number of requests; outstanding requests in the queue should rarely, if ever reach this maximum value.

If the maximum Queue Length is reached, WebLogic Server automatically doubles the size of the queue to account for the additional work. Exceeding 65536 requests in the queue indicates a problem with the threads in the queue, rather than the length of the queue itself; check for stuck threads or an insufficient thread count in the execute queue.

Queue Length Threshold Percent—The percentage (from 1–99) of the Queue Length size that can be reached before the server indicates an overflow condition for the queue. All actual queue length sizes below the threshold percentage are considered normal; sizes above the threshold percentage indicate an overflow. When an overflow condition is reached, WebLogic Server logs an error message and increases the number of threads in the queue by the value of the Threads Increase attribute to help reduce the workload.

By default, the Queue Length Threshold Percent value is 90 percent. In most situations, you should leave the value at or near 90 percent, to account for any potential condition where additional threads may be needed to handle an unexpected spike in work requests. Keep in mind that Queue Length Threshold Percent must not be used as an automatic tuning parameter—the threshold should never trigger an increase in thread count under normal operating conditions.

Thread Count—The number of threads assigned to this queue. If you do not need to use more than 15 threads (the default) for your work, do not change the value of this attribute. (For more information, see Should You Modify the Default Thread Count?.)

Threads Increase—The number of threads WebLogic Server should add to this execute queue when it detects an overflow condition. If you specify zero threads (the default), the server changes its health state to "warning" in response to an overflow condition in the thread, but it does not allocate additional threads to reduce the workload.

Note:

If WebLogic Server increases the number of threads in response to an overflow condition, the additional threads remain in the execute queue until the server is rebooted. Monitor the error log to determine the cause of overflow conditions, and reconfigure the thread count as necessary to prevent similar conditions in the future. Do not use the combination of Threads Increase and Queue Length Threshold Percent as an automatic tuning tool; doing so generally results in the execute queue allocating more threads than necessary and suffering from poor performance due to context switching.

Threads Minimum—The minimum number of threads that WebLogic Server should maintain in this execute queue to prevent unnecessary overflow conditions. By default, the Threads Minimum is set to 5.

Threads Maximum—The maximum number of threads that this execute queue can have; this value prevents WebLogic Server from creating an overly high thread count in the queue in response to continual overflow conditions. By default, the Threads Maximum is set to 400.

8. Click Save.

9. To activate these changes, in the Change Center of the Administration Console, click Activate Changes. Not all changes take effect immediately—some require a restart.

10. You must reboot the server to use the new thread detection behavior values.

Modifying the Thread Count

To modify the default execute queue thread count using the Administration Console:

1. If you have not already done so, in the Change Center of the Administration Console, click Lock & Edit.

2. In the left pane of the console, expand Environment > Servers.

3. On the Summary of Servers page, select the server instance for which you will configure thread detection behavior.

4. On the Configuration > Queues tab, select the execute queue for which you will modify the default thread count.

5. You can only modify the default execute queue for the server or a user-defined execute queue.

6. Locate the Thread Count value and increase or decrease it, as appropriate.

7. Click Save.

8. To activate these changes, in the Change Center of the Administration Console, click Activate Changes. Not all changes take effect immediately—some require a restart.

9. You must reboot the server to use the new thread detection behavior values.

Tuning Execute Queues for Overflow Conditions

You can configure WebLogic Server to detect and optionally address potential overflow conditions in the default execute queue or any user-defined execute queue. WebLogic Server considers a queue to have a possible overflow condition when its current size reaches a user-defined percentage of its maximum size. When this threshold is reached, the server changes its health state to "warning" and can optionally allocate additional threads to perform the outstanding work in the queue, thereby reducing the queue length.

To automatically detect and address overflow conditions in a queue, you can configure the following items:

- The threshold at which the server indicates an overflow condition. This value is set as a percentage of the configured size of the execute queue (the QueueLength value).

- The number of threads to add to the execute queue when an overflow condition is detected. These additional threads work to reduce the size of the queue and reduce the size of the queue to its normal operating size.

- The minimum and maximum number of threads available to the queue. In particular, setting the maximum number of threads prevents the server from assigning an overly high thread count in response to overload conditions.

To tune an execute queue using the WebLogic Server Administration Console:

1. If you have not already done so, in the Change Center of the Administration Console, click Lock & Edit.

2. In the left pane of the console, expand Environment > Servers.

3. On the Summary of Servers page, select the server instance for which you will configure overflow conditions behavior.

4. Select the Configuration > Queues tab, select the execute queue for which you will configure overflow conditions behavior.

5. Specify how the server instance should detect an overflow condition for the selected queue by modifying the following attributes:
Queue Length—Specifies the maximum number of simultaneous requests that the server can hold in the queue. The default of 65536 requests represents a very large number of requests; outstanding requests in the queue should rarely, if ever reach this maximum value. Always leave the Queue Length at the default value of 65536 entries.

Queue Length Threshold Percent—The percentage (from 1–99) of the Queue Length size that can be reached before the server indicates an overflow condition for the queue. All actual queue length sizes below the threshold percentage are considered normal; sizes above the threshold percentage indicate an overflow. By default, the Queue Length Threshold Percent is set to 90 percent.

6. To specify how this server should address an overflow condition for the selected queue, modify the following attribute:
Threads Increase—The number of threads WebLogic Server should add to this execute queue when it detects an overflow condition. If you specify zero threads (the default), the server changes its health state to "warning" in response to an overflow condition in the execute queue, but it does not allocate additional threads to reduce the workload.

7. To fine-tune the variable thread count of this execute queue, modify the following attributes:
Threads Minimum—The minimum number of threads that WebLogic Server should maintain in this execute queue to prevent unnecessary overflow conditions. By default, the Threads Minimum is set to 5.

Threads Maximum—The maximum number of threads that this execute queue can have; this value prevents WebLogic Server from creating an overly high thread count in the queue in response to continual overflow conditions. By default, the Threads Maximum is set to 400.

8. Click Save.

9. To activate these changes, in the Change Center of the Administration Console, click Activate Changes. Not all changes take effect immediately—some require a restart.

10. You must reboot the server to use the new thread detection behavior values.

Assigning Servlets and JSPs to Execute Queues

You can assign a servlet or JSP to a configured execute queue by identifying the execute queue name in the initialization parameters. Initialization parameters appear within the init-param element of the servlet's or JSP's deployment descriptor file, web.xml. To assign an execute queue, enter the queue name as the value of the wl-dispatch-policy parameter, as in the example:

<servlet>
<servlet-name>MainServlet</servlet-name>
<jsp-file>/myapplication/critical.jsp</jsp-file>
<init-param>
<param-name>wl-dispatch-policy</param-name>
<param-value>CriticalAppQueue</param-value>
</init-param>
</servlet>

See "Creating and Configuring Servlets" in Developing Web Applications, Servlets, and JSPs for Oracle WebLogic Server for more information about specifying initialization parameters in web.xml.

Assigning EJBs and RMI Objects to Execute Queues

To assign an EJB object to a configured execute queue, use the new dispatch-policy element in weblogic-ejb-jar.xml. For more information, see the weblogic-ejb-jar.xml Deployment Descriptor.

While you can also set the dispatch policy through the appc compiler -dispatchPolicy flag, Oracle strongly recommends you use the deployment descriptor element instead. This way, if the EJB is recompiled, during deployment for example, the setting will not be lost.

To assign an RMI object to a configured execute queue, use the -dispatchPolicy option to the rmic compiler. For example:

java weblogic.rmic -dispatchPolicy CriticalAppQueue ...

Monitoring Execute Threads

To use the Administration Console to monitor the status of execute threads:

1. If you have not already done so, in the Change Center of the Administration Console, click Lock & Edit.

2. In the left pane of the console, expand Environment > Servers.

3. On the Summary of Servers page, select the server instance for which you will configure thread detection behavior.

4. Select the Monitoring > Threads tab.

5. A table of the execute queues available on this server instance is displayed.

6. Select an execute queue for which you would like to view thread information.

7. A table of execute threads for the selected execute queue is displayed.

Allocating Execute Threads to Act as Socket Readers

For best performance, Oracle recommends that you use the native socket reader implementation, rather than the pure-Java implementation, on machines that host WebLogic Server instances (see Thread Management). However, if you must use the pure-Java socket reader implementation for host machines, you can still improve the performance of socket communication by configuring the proper number of execute threads to act as socket reader threads for each server instance.

The ThreadPoolPercentSocketReaders attribute sets the maximum percentage of execute threads that are set to read messages from a socket. The optimal value for this attribute is application-specific. The default value is 33, and the valid range is 1–99.

Allocating execute threads to act as socket reader threads increases the speed and the ability of the server to accept client requests. It is essential to balance the number of execute threads that are devoted to reading messages from a socket and those threads that perform the actual execution of tasks in the server.

Setting the Number of Socket Reader Threads For a Server Instance

To use the Administration Console to set the maximum percentage of execute threads that read messages from a socket:

1. If you have not already done so, in the Change Center of the Administration Console, click Lock & Edit.

2. In the left pane of the console, expand Environment > Servers.

3. On the Summary of Servers page, select the server instance for which you will configure thread detection behavior.

4. Select the Configuration > Tuning tab.

5. Specify the percentage of Java reader threads in the Socket Readers field. The number of Java socket readers is computed as a percentage of the number of total execute threads (as shown in the Thread Count field for the Execute Queue).

6. Click Save.

7. To activate these changes, in the Change Center of the Administration Console, click Activate Changes.

Setting the Number of Socket Reader Threads on Client Machines

On client machines, you can configure the number of available socket reader threads in the JVM that runs the client. Specify the socket readers by defining the following parameters in the java command line for the client:

-Dweblogic.ThreadPoolSize=value
-Dweblogic.ThreadPoolPercentSocketReaders=value

Tuning the Stuck Thread Detection Behavior

WebLogic Server automatically detects when a thread in an execute queue becomes "stuck." Because a stuck thread cannot complete its current work or accept new work, the server logs a message each time it diagnoses a stuck thread.

WebLogic Server diagnoses a thread as stuck if it is continually working (not idle) for a set period of time. You can tune a server's thread detection behavior by changing the length of time before a thread is diagnosed as stuck, and by changing the frequency with which the server checks for stuck threads. Although you can change the criteria WebLogic Server uses to determine whether a thread is stuck, you cannot change the default behavior of setting the "warning" and "critical" health states when all threads in a particular execute queue become stuck. For more information, see "Understanding WebLogic Logging Services" in Configuring Log Files and Filtering Log Messages for Oracle WebLogic Server.

To configure stuck thread detection behavior:

1. If you have not already done so, in the Change Center of the Administration Console, click Lock & Edit.

2. In the left pane of the console, expand Environment > Servers.

3. On the Summary of Servers page, select the server instance for which you will configure thread detection behavior.

4. On the Configuration > Tuning tab, update as necessary:
Stuck Thread Max Time—Amount of time, in seconds, that a thread must be continually working before a server instance diagnoses a thread as being stuck.

Stuck Thread Timer Interval—Amount of time, in seconds, after which a server instance periodically scans threads to see if they have been continually working for the configured Stuck Thread Max Time.

5. Click Save.

6. To activate these changes, in the Change Center of the Administration Console, click Activate Changes. Not all changes take effect immediately—some require a restart.

7. You must reboot the server to use the new thread detection behavior values.

B Capacity Planning

This chapter provides an introduction to capacity planning. Capacity planning is the process of determining what type of hardware and software configuration is required to meet application needs adequately. Capacity planning is not an exact science. Every application is different and every user behavior is different.

- Capacity Planning Factors

- Assessing Your Application Performance Objectives

- Hardware Tuning

- Network Performance

- Related Information

Capacity Planning Factors

A number of factors influence how much capacity a given hardware configuration will need in order to support a WebLogic Server instance and a given application. The hardware capacity required to support your application depends on the specifics of the application and configuration. You should consider how each of these factors applies to your configuration and application.

The following sections discuss several of these factors. Understanding these factors and considering the requirements of your application will aid you in generating server hardware requirements for your configuration. Consider the capacity planning questions in Table B-1.

Table B-1 Capacity Planning Factors and Information Reference

Capacity Planning Questions

For Information, See:

Is WebLogic Server well-tuned?

Assessing Your Application Performance Objectives

How well-designed is the user application?

Database Server Capacity and User Storage Requirements

Is there enough bandwidth?

Network Load

How many transactions need to run simultaneously?

Concurrent Sessions

Is the database a limiting factor? Are there additional user storage requirements?

Database Server Capacity and User Storage Requirements

What is running on the machine in addition to WebLogic Server?

Network Load

Do clients use SSL to connect to WebLogic Server?

SSL Connections and Performance

What types of traffic do the clients generate?

RMI and Server Traffic

What types of clients connect to the WebLogic Server application?

Programmatic and Web-based Clients

Is your deployment configured for a cluster?

Clustered Configurations

Are your servers configured for migration?

Server Migration

Programmatic and Web-based Clients

Primarily, two types of clients can connect to WebLogic Server:

- Web-based clients, such as Web browsers and HTTP proxies, use the HTTP or HTTPS (secure) protocol to obtain HTML or servlet output.

- Programmatic clients, such as Java applications and applets, can connect through the T3 protocol and use RMI to connect to the server.

The stateless nature of HTTP requires that the server handle more overhead than is the case with programmatic clients. However, the benefits of HTTP clients are numerous, such as the availability of browsers and firewall compatibility, and are usually worth the performance costs.

Programmatic clients are generally more efficient than HTTP clients because T3 does more of the presentation work on the client side. Programmatic clients typically call directly into EJBs while Web clients usually go through servlets. This eliminates the work the server must do for presentation. The T3 protocol operates using sockets and has a long-standing connection to the server.

A WebLogic Server installation that relies only on programmatic clients should be able to handle more concurrent clients than an HTTP proxy that is serving installations. If you are tunneling T3 over HTTP, you should not expect this performance benefit. In fact, performance of T3 over HTTP is generally 15 percent worse than typical HTTP and similarly reduces the optimum capacity of your WebLogic Server installation.

RMI and Server Traffic

What types of server traffic do the clients generate? If you are using T3 clients, most interaction with the server involves Remote Method Invocation (RMI.) Clients using RMI do not generate heavy traffic to the server because there is only one sender and one listener.

RMI can use HTTP tunneling to allow RMI calls to traverse a firewall. RMI tunneled through HTTP often does not deliver the higher degree of performance provided by non-tunneled RMI.

SSL Connections and Performance

Secure sockets layer (SSL) is a standard for secure Internet communications. WebLogic Server security services support X.509 digital certificates and access control lists (ACLs) to authenticate participants and manage access to network services. For example, SSL can protect JSP pages listing employee salaries, blocking access to confidential information.

SSL involves intensive computing operations. When supporting the cryptography operations in the SSL protocol, WebLogic Server can not handle as many simultaneous connections.

The number of SSL connections required out of the total number of clients required. Typically, for every SSL connection that the server can handle, it can handle three non-SSL connections. SSL substantially reduces the capacity of the server depending upon the strength of encryption used in the SSL connections. Also, the amount of overhead SSL imposes is related to how many client interactions have SSL enabled. WebLogic Server includes native performance packs for SSL operations.

WebLogic Server Process Load

What is running on the machine in addition to a WebLogic Server? The machine may be processing much more than presentation and business logic. For example, it could be running a Web server or maintaining a remote information feed, such as a stock information feed from a quote service.

Consider how much of your WebLogic Server machine's processing power is consumed by processes unrelated to WebLogic Server. In the case in which WebLogic Server (or the machine on which it resides) is doing substantial additional work, you need to determine how much processing power will be drained by other processes. When a Web server proxy is running on the same machine as WebLogic Server, expect anywhere from 25 to 50 percent of the computing capacity.

Database Server Capacity and User Storage Requirements

Is the database a bottleneck? Are there additional user storage requirements? Often the database server runs out of capacity much sooner that WebLogic Server does. Plan for a database that is sufficiently robust to handle the application. Typically, a good application's database requires hardware three to four times more powerful than the application server hardware. It is good practice to use a separate machine for your database server.

Generally, you can tell if your database is the bottleneck if you are unable to maintain WebLogic Server CPU usage in the 85 to 95 percent range. This indicates that WebLogic Server is often idle and waiting for the database to return results. With load balancing in a cluster, the CPU utilization across the nodes should be about even.

Some database vendors are beginning to provide capacity planning information for application servers. Frequently this is a response to the three-tier model for applications.

An application might require user storage for operations that do not interact with a database. For example, in a secure system disk and memory are required to store security information for each user. You should calculate the size required to store one user's information, and multiply by the maximum number of expected users.

Concurrent Sessions

How many transactions must run concurrently? Determine the maximum number of concurrent sessions WebLogic Server will be called upon to handle. For each session, you will need to add more RAM for efficiency. Oracle recommends that you install a minimum of 256 MB of memory for each WebLogic Server installation that will be handling more than minimal capacity.

Next, research the maximum number of clients that will make requests at the same time, and how frequently each client will be making a request. The number of user interactions per second with WebLogic Server represents the total number of interactions that should be handled per second by a given WebLogic Server deployment. Typically for Web deployments, user interactions access JSP pages or servlets. User interactions in application deployments typically access EJBs.

Consider also the maximum number of transactions in a given period to handle spikes in demand. For example, in a stock report application, plan for a surge after the stock market opens and before it closes. If your company is broadcasting a Web site as part of an advertisement during the World Series or World Cup Soccer playoffs, you should expect spikes in demand.

Network Load

Is the bandwidth sufficient? WebLogic Server requires enough bandwidth to handle all connections from clients. In the case of programmatic clients, each client JVM will have a single socket to the server. Each socket requires bandwidth. A WebLogic Server handling programmatic clients should have 125 to 150 percent the bandwidth that a server with Web-based clients would handle. If you are interested in the bandwidth required to run a web server, you can assume that each 56kbps (kilobits per second) of bandwidth can handle between seven and ten simultaneous requests depending upon the size of the content that you are delivering. If you are handling only HTTP clients, expect a similar bandwidth requirement as a Web server serving static pages.

The primary factor affecting the requirements for a LAN infrastructure is the use of replicated sessions for servlets and stateful session EJBs. In a cluster, replicated sessions are the biggest consumer of LAN bandwidth. Consider whether your application will require the replication of session information for servlets and EJBs.

To determine whether you have enough bandwidth in a given deployment, look at the network tools provided by your network operating system vendor. In most cases, including Windows NT, Windows 2000, and Solaris, you can inspect the load on the network system. If the load is very high, bandwidth may be a bottleneck for your system.

Clustered Configurations

Clusters greatly improve efficiency and failover. Customers using clustering should not see any noticeable performance degradation. A number of WebLogic Server deployments in production involve placing a cluster of WebLogic Server instances on a single multiprocessor server.

Large clusters performing replicated sessions for Enterprise JavaBeans (EJBs) or servlets require more bandwidth than smaller clusters. Consider the size of session data and the size of the cluster.

Server Migration

Are your servers configured for migration? Migration in WebLogic Server is the process of moving a clustered WebLogic Server instance or a component running on a clustered instance elsewhere in the event of failure. In the case of whole server migration, the server instance is migrated to a different physical machine upon failure, either manually or automatically.

For capacity planning in a production environment, keep in mind that server startup during migration taxes CPU utilization. You cannot assume that because a machine can handle x number of servers running concurrently that it also can handle that same number of servers starting up on the same machine at the same time.

Application Design

How well-designed is the application? WebLogic Server is a platform for user applications. Badly designed or unoptimized user applications can drastically slow down the performance of a given configuration from 10 to 50 percent. The prudent course is to assume that every application that is developed for WebLogic Server will not be optimal and will not perform as well as benchmark applications. Increase the maximum capacity that you calculate or expect. See Tune Your Application.

Assessing Your Application Performance Objectives

At this stage in capacity planning, you gather information about the level of activity expected on your server, the anticipated number of users, the number of requests, acceptable response time, and preferred hardware configuration. Capacity planning for server hardware should focus on maximum performance requirements and set measurable objectives for capacity.

The numbers that you calculate from using one of our sample applications are of course just a rough approximation of what you may see with your application. There is no substitute for benchmarking with the actual production application using production hardware. In particular, your application may reveal subtle contention or other issues not captured by our test applications.

Hardware Tuning

When you examine performance, a number of factors influence how much capacity a given hardware configuration will need in order to support WebLogic Server and a given application. The hardware capacity required to support your application depends on the specifics of the application and configuration. You should consider how each factor applies to your configuration and application.

Benchmarks for Evaluating Performance

The Standard Performance Evaluation Corporation, at http://www.spec.org, provides a set of standardized benchmarks and metrics for evaluating computer system performance.

Supported Platforms

See "Supported Configurations" in What's New in Oracle WebLogic Server for links to the latest certification information on the hardware/operating system platforms that are supported for each release of WebLogic Server.

Network Performance

Network performance is affected when the supply of resources is unable to keep up with the demand for resources. Today's enterprise-level networks are very fast and are now rarely the direct cause of performance in well-designed applications. However, if you find that you have a problem with one or more network components (hardware or software), work with your network administrator to isolate and eliminate the problem. You should also verify that you have an appropriate amount of network bandwidth available for WebLogic Server and the connections it makes to other tiers in your architecture, such as client and database connections. Therefore, it is important to continually monitor your network performance to troubleshoot potential performance bottlenecks.

Determining Network Bandwidth

A common definition of bandwidth is "the rate of the data communications transmission, usually measured in bits-per-second, which is the capacity of the link to send and receive communications." A machine running WebLogic Server requires enough network bandwidth to handle all WebLogic Server client connections. In the case of programmatic clients, each client JVM has a single socket to the server, and each socket requires dedicated bandwidth. A WebLogic Server instance handling programmatic clients should have 125–150 percent of the bandwidth that a similar Web server would handle. If you are handling only HTTP clients, expect a bandwidth requirement similar to a Web server serving static pages.

To determine whether you have enough bandwidth in a given deployment, you can use the network monitoring tools provided by your network operating system vendor to see what the load is on the network system. You can also use common operating system tools, such as the netstat command for Solaris or the System Monitor (perfmon) for Windows, to monitor your network utilization. If the load is very high, bandwidth may be a bottleneck for your system.

Also monitor the amount of data being transferred across the your network by checking the data transferred between the application and the application server, and between the application server and the database server. This amount should not exceed your network bandwidth; otherwise, your network becomes the bottleneck. To verify this, monitor the network statistics for retransmission and duplicate packets, as follows:

netstat -s -P tcp

Related Information

The Oracle corporate Web site provides all documentation for WebLogic Server.

Information on topics related to capacity planning is available from numerous third-party software sources, including the following:

- "Capacity Planning for Web Performance: Metrics, Models, and Methods". Prentice Hall, 1998, ISBN 0-13-693822-1 at http://www.cs.gmu.edu/~menasce/webbook/index.html.

- "Configuration and Capacity Planning for Solaris Servers" at http://btobsearch.barnesandnoble.com/booksearch/isbninquiry.asp?userid=36YYSNN1TN&isbn=0133499529&TXT=Y&itm=1, Brian L. L. Wong.

- "J2EE Applications and BEA WebLogic Server". Prentice Hall, 2001, ISBN 0-13-091111-9 at http://www.amazon.com/J2EE-Applications-BEA-WebLogic-Server/dp/0130911119.

- Web portal focusing on capacity-planning issues for enterprise application deployments at http://www.capacityplanning.com/.

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