6 Using the WebLogic Persistent Store

The following sections explain how to configure and monitor the persistent store, which provides a built-in, high-performance storage solution for WebLogic Server subsystems and services that require persistence.

Overview of the Persistent Store
Using the Default Persistent Store
Using Custom File Stores and JDBC Stores
Creating a Custom (User-Defined) File Store
Guidelines for Configuring a Synchronous Write Policy
Creating a JDBC Store
Guidelines for Configuring a JDBC Store
Monitoring a Persistent Store
Administering a Persistent Store
Limitations of the Persistent Store

Overview of the Persistent Store

The persistent store provides a built-in, high-performance storage solution for WebLogic Server subsystems and services that require persistence. For example, it can store persistent JMS messages or temporarily store messages sent using the Store-and-Forward feature. The persistent store supports persistence to a file-based store or to a JDBC-enabled database.

Table 6-1 defines many of the WebLogic services and subsystems that can create connections to the persistent store. Each subsystem that uses the persistent store specifies a unique connection ID that identifies that subsystem.

Table 6-1 Persistent Store Users

Subsystem/Service	What It Stores	More Information
Diagnostic Service	Log records, data events, and harvested metrics.	"Understanding WLDF Configuration" in Configuring and Using the Diagnostics Framework for Oracle WebLogic Server
JMS Messages	Persistent messages and durable subscribers.	"Understanding the Messaging Models" in Programming JMS for Oracle WebLogic Server
JMS Paging Store	One per JMS server. Paged persistent and non-persistent messages.	"Main Steps for Configuring Basic JMS System Resources" in Configuring and Managing JMS for Oracle WebLogic Server.
JTA Transaction Log (TLOG)	Information about committed transactions coordinated by the server that may not have been completed.	"Managing Transactions" in Programming JTA for Oracle WebLogic Server
Path Service	The mapping of a group of messages to a messaging resource.	"Using the WebLogic Path Service" in Configuring and Managing JMS for Oracle WebLogic Server
Store-and-Forward (SAF) Service Agents	Messages for a sending SAF agent for retransmission to a receiving SAF agent	"Understanding the Store-and-Forward Service" in Configuring and Managing Store-and-Forward for Oracle WebLogic Server.
Web Services	Request and response SOAP messages from an invocation of a reliable WebLogic Web Service.	"Using Reliable SOAP Messaging" in Programming Advanced Features of JAX-RPC Web Services for Oracle WebLogic Server
EJB Timer Services	EJB Timer objects.	"Understanding Enterprise JavaBeans" in Programming WebLogic Enterprise JavaBeans for Oracle WebLogic Server

For more information about the store connection IDs, see Monitoring Store Connections.

Features of the Persistent Store

The key features of the persistent store include:

Default file store for each server instance that requires no configuration.
One store is shareable by multiple subsystems, as long as they are all targeted to the same server instance or migratable target.
High-performance throughput and transactional support.
Modifiable parameters that let you create customized file stores and JDBC stores.
Monitoring capabilities for persistent store statistics and open store connections.
In a clustered environment, a customized store can be migrated from an unhealthy server to a backup server, either on the whole-server level or on the service level.

High-Performance Throughput and Transactional Support

Throughput is the main performance goal of the persistent store. Multiple subsystems can share the same persistent store, as long as they are all targeted to the same server instance or migratable target.

This is a performance advantage because the persistent store is treated as a single resource by the transaction manager for a particular transaction, even if the transaction involves multiple services that use the same store. For example, if JMS and EJB timers share a store, and a JMS message and an EJB timer are created in a single transaction, the transaction will be one-phase and incur a single resource write, rather than two-phase, which incurs four resource writes (two on each resource), plus a transaction entry write (on the transaction log).

Both the file store and the JDBC store can survive a process crash or hardware power failure without losing any committed updates. Uncommitted updates may be retained or lost, but in no case will a transaction be left partially complete after a crash.

Comparing File Stores and JDBC Stores

The following are some similarities and differences between file stores and JDBC stores:

The default persistent store can only be a file store. Therefore, a JDBC store cannot be used as a default persistent store.
The transaction log (TLOG) can only be stored in a default store.
Both have the same transaction semantics and guarantees. As with JDBC store writes, file store writes are guaranteed to be persisted to disk and are not simply left in an intermediate (that is, unsafe) cache.
Both have the same application interface (no difference in application code).
All things being equal, file stores generally offer better throughput than a JDBC store.

Note:
If a database is running on high-end hardware with very fast disks, and WebLogic Server is running on slower hardware or with slower disks, then you may get better performance from the JDBC store.
File stores are generally easier to configure and administer, and do not require that WebLogic subsystems depend on any external component.
File stores generate no network traffic; whereas, JDBC stores will generate network traffic if the database is on a different machine from WebLogic Server.
JDBC stores may make it easier to handle failure recovery since the JDBC interface can access the database from any machine on the same network. With the file store, the disk must be shared or migrated.

Securing File Store Data

In order to properly secure file store data, you must set appropriate directory permissions on all your file store directories. If you require data encryption, you must use appropriate third-party encryption software.

High Availability For Persistent Stores

For high availability, a persistent file-based store (default or custom) can be migrated along with its parent server as part of the "whole server-level" migration feature, which provides both automatic and manual migration at the server level, rather than on the service level. For more information, see "Whole Server Migration" in Using Clusters for Oracle WebLogic Server. However, file-based stores must be configured on a shared disk that is available to the migratable target servers in the cluster.

Persistent Store Migration

File-based stores and JDBC-accessible stores can also be migrated as part of a "service-level" migration for JMS-related services, such as stores, JMS servers, SAF agents, and the path service, which rely on stores to maintain data. Service-level migration is controlled by a migratable target, which serves as a grouping of JMS-related services, and which is hosted on only one physical server in a cluster. Such hosted services can be automatically migrated from the current unhealthy hosting server to a healthy active server with the help of the Health Monitoring subsystem. JMS services hosted by a migratable target can also be manually migrated, either in response to a server failure or as part of regularly scheduled server maintenance. When the migratable target is migrated, all pinned services hosted by that target are also migrated. For more information on service-level migration, see "Service Migration" in Using Clusters for Oracle WebLogic Server.

Migratable JMS-related services cannot use the default file store, so you must configure a custom file store or JDBC store and target it to the same migratable target as the JMS server, SAF agent, or path service associated with the store.

Note:

As a best practice, a path service should use its own custom store and migratable target.

Migratable file stores must also either be configured on a shared disk that is available to the migratable targets in the cluster or you can use pre/post-migration scripts to migrate a file store's data to a backup server. See "Custom Store Availability for JMS Services" in Using Clusters for Oracle WebLogic Server.

High Availability Storage Solutions

If you have applications that need access to persistent stores that reside on remote machines after the migration of a JMS server or JTA transaction log, then you should implement one of the following highly-available storage solutions:

File-based stores (default or custom)—Implement a hardware solution, such as a dual-ported SCSI disk or Storage Area Network (SAN) to make a file store available from shareable disks or remote machines.

Note:
If a file store is disconnected and re-connected again, its host server instance must be rebooted to successfully continue sending/receiving persistent JMS messages. For example, if for some reason the file system containing a file store is unmounted and then remounted, attempts to send persistent JMS messages will generate JMS exceptions until the host server is rebooted.
JDBC-accessible stores—Configure a JDBC store and use JDBC to access this store, which can be on yet another server. Applications can then take advantage of any high-availability or failover solutions offered by your database vendor. In addition, JDBC stores support multi data sources, which provide failover between nodes of a highly available database system, such as redundant databases or Oracle Real Application Clusters (Oracle RAC). For more information about using JDBC multi data sources, see "Configuring JDBC Multi Data Sources" in Configuring and Managing JDBC for Oracle WebLogic Server.
Any persistent store—Use high-availability clustering software such as VERITAS™ Cluster Server, which provides an integrated, out-of-the-box solution for WebLogic Server-based applications. Another recommended high-availability software solution is IBM HACMP or the equivalent.

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 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.

The default store can be configured by directly manipulating DefaultFileStoreMBean parameters. If this MBean is not defined in the domain configuration file, then the configuration subsystem ensures that the DefaultFileStoreMBean always exists with the default values.

Also, the Administration Console enables you to change the default store parameters, such as its default directory location and Synchronous Write Policy, as described in "Modify the Default Store Settings" in the Oracle WebLogic Server Administration Console Help.

In addition to using the default file store, you can also configure a custom file store or JDBC store to suit your specific needs, as explained in Using Custom File Stores and JDBC Stores. One exception, however, is the JTA transaction log (TLOG), which always uses the default store. This is because the transaction log must always be available early in the server boot process. For more information about the TLOG, see "Transaction Log Files" in Programming JTA for Oracle WebLogic Server.

Default Store Location

The default store maintains its data in a data\store\default directory inside the servername subdirectory of a domain's root directory

For example, if no directory name is specified for the default file store, it defaults to:

MW_HOME\user_projects\domains\domain-name\servers\server-name\data\store\default

where domainname is the root directory of your domain, typically c:\oracle\user_projects\domains\domainname, which is parallel to the directory in which WebLogic Server program files are stored, typically c:\oracle\wlserver_10.3.

You can, however, specify another location for the default store by directly manipulating the DefaultFileStoreMBean parameters or by using the Administration Console, as described in "Modify the Default Store Settings" in the Oracle WebLogic Server Administration Console Help.

Example of a Default File Store

Here's an example of how a default file store may look in a domain's configuration file, with the default directory location and Synchronous Write Policy settings overridden:

<server
  <name>myserver</name>
  <default-file-store>
  <directory>C:/store</directory>
  <synchronous-write-policy>Disabled</synchronous-write-policy>
  </default-file-store>
</server>

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 or when you want a JMS service that accesses a file store to be able to migrate with the store to another server member in a cluster. 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. JDBC stores also support migratable targets for automatic or manual JMS service migration.

For more information about configuring a persistent store, see When to Use a Custom Persistent Store.

When to Use a Custom Persistent Store

WebLogic Server provides configuration options for creating a custom file store or JDBC store. For example, you may want to:

Place a file store's files on a particular device.
Use a JDBC store rather than a file store for a particular server instance.
Allow all physical stores in a cluster to share the same logical name.
Logically separate different services to use different files or tables. (This may simplify administration and maintenance at the expense of reduced performance.)
Migratable JMS-related services cannot use the default persistent store, so you must configure a custom store and target it to the same migratable target as the migratable JMS service. For more information, see "Service Migration" in Using Clusters for Oracle WebLogic Server.

Methods of Creating a Custom Persistent Store

A user-defined persistent store can be configured in the following ways:

Use the Administration Console to configure a custom file store or JDBC store, as described in "Configure Persistent Stores" in the Oracle WebLogic Server Administration Console Help.
Directly edit the configuration file (config.xml) of the server instance that is hosting the default persistent store.
Use the WebLogic Java Management Extensions (JMX) to create persistent stores. JMX is the Java EE solution for monitoring and managing resources on a network. For more information see, Developing Custom Management Utilities With JMX for Oracle WebLogic Server.
Use the WebLogic Scripting Tool (WLST) to create persistent stores. WLST is a command-line scripting interface that you use to interact with and configure WebLogic Server instances and domains. For more information, see Oracle WebLogic Scripting Tool.
Use the WebLogic Configuration Wizard to change the options of the default persistent store. For detailed information on how to use the Configuration Wizard to configure a persistent store, see "Creating a WebLogic Domain" in Creating Domains Using the Configuration Wizard.

Modifying Custom Persistent Store Parameters

Modifying certain custom store configuration options, such as a JDBC store's prefix or a file store's directory, do not necessarily require a server restart if you do the following:

Set the targets of any dependent services to null (such as a JMS server that uses the custom store), and then setting the custom store target to null. (Setting a service's target to null implicitly shuts down the service.)
Reverse the process by setting the custom store target back to its original value and then setting the dependent resource targets back to their original values.

In cases where the custom store and JMS servers share a migratable target, you can administratively restart the migratable target.

Creating a Custom (User-Defined) File Store

The following sections provide an example of a custom file store and configuration guidelines for choosing a synchronous write policy.

To create a custom file store, you can directly modify the default FileStoreMBean parameters. For instructions on using the Administration Console to create a custom file store, see "Create File Stores" in the Oracle WebLogic Server Administration Console Help.

Main Steps for Configuring a Custom File Store

The main steps for creating a custom file store are as follows:

Create a directory where the file store's data will be persisted.
Create a custom file store and specify the directory location that you created.
Associate the custom file store with the subsystem(s) or migratable target that will be accessing it, such as:
- For JMS servers, select the custom file store on the General Configuration page.
- For Store-and-Forward agents, select the custom file store on the General Configuration page.
- For a Path Service, select the custom file store on the General Configuration page.

Example of a Custom File Store

Here's an example of how a custom file store may look in a domain's configuration file with its files kept in a /disk1/jmslog directory.

<file-store>
  <name>SampleFileStore</name>
  <target>myserver</target>
  <directory>/disk1/jmslog</directory>
</file-store>

Table 6-2 briefly describes the file store configuration parameters that can be modified.

Table 6-2 Custom File Store Configuration Options

Option	Required	What It Does
Name	Yes	The name of the file store, which must be unique across all stores in the domain.
Targets	Yes	The server instance or migratable target where a file store is targeted. Multiple subsystems can share the same file store, as long as they are all targeted to the same server instance or migratable target. Note: When using migratable targets for JMS services, you must target the file store to the same migratable target used by the JMS service. See "Service Migration" in Using Clusters for Oracle WebLogic Server.
Directory	Yes	The path name to the directory on the file system where the file store is kept. Note: When targeting a file store to a migratable target, the store directory must be accessible from all candidate server members in the migratable target. For highest availability, use either a SAN (Storage Area Network) or a dual-ported SCSI disk. See "Service Migration" in Using Clusters for Oracle WebLogic Server. Modifying an existing file store's directory does not necessarily require a server restart, as described in Modifying Custom Persistent Store Parameters.
CacheDirectory	No	This setting only applies for the `Direct-Write-With-Cache` file store synchronous write policy. See Guidelines for Configuring a Synchronous Write Policy..
Logical Name	No	Optionally used with subsystems, like EJBs, when deploying a module to an entire cluster, but also require a different physical store on each server instance in the cluster. In such a configuration, each physical store would have its own name, but all the persistent stores would share the same logical name.
Synchronous Write Policy	No	Defines the IO behavior of a file store including immediate durability of individual write operations. Values are: Direct-Write (default), Direct-Write-With-Cache, Cache-Flush, and Disabled. For more information, see Guidelines for Configuring a Synchronous Write Policy.

For instructions on configuring a custom file store using the Administration Console, see "Create File Stores" in the Oracle WebLogic Server Administration Console Help.

Guidelines for Configuring a Synchronous Write Policy

There are several Synchronous Write Policies available for file stores. The Synchronous Write Policy determines the behavior of the write operation of the file store. You should select a policy that best suits your environment and meets your needs for runtime performance and data integrity after a possible crash. See "Tuning the WebLogic Persistent Store" in Performance and Tuning for Oracle WebLogic Server for more details about tuning and performance specifics of Synchronous Write Policy and other file store options.

Note:

To view a running custom or default file store's synchronous write policy and driver, check the WL-280008 and WL-280009 messages in the server log.

Direct-Write-With-Cache Policy

For most scenarios, Oracle recommends using the Direct-Write-With-Cache policy. When this policy is selected, WebLogic Server writes synchronously to a primary set of files in the location defined by the Directory attribute of the file store configuration using a native I/O wlfileio driver. WebLogic Server also asynchronously writes to a corresponding cache file in the location defined by the CacheDirectory attribute of the file store configuration, which is done implicitly by using OS memory caching the cache file blocks as output buffers for the primary data file. The cache files are used for performance optimizations at runtime and boot time and for recovery. This combination of direct writing with a native file driver and the use of corresponding cache files typically provides the best overall performance with the most safe disk writes.

This option uses approximately twice as much disk space as other policies and stores files in two locations. You may need to consider disk space allocations in these locations and you may need to secure both of these locations.

When configuring file locations with the Direct-Write-With-Cache policy, the location of the CacheDirectory attribute should be a local directory, even when configuring for high availability (Whole Server Migration or Automatic Service Migration). The cache files are used for performance optimizations only. The true persistent storage for messages is defined by the Directory attribute of the file store configuration. Only that directory needs to be available to the migrated WebLogic Server instance or JMS service after migration. The same applies to disaster recovery scenarios: only the files defined in the Directory location need to replicated to the backup site.

Notes:

If the file store native wlfileio driver cannot be loaded, the store automatically runs in an alternate specialized Direct-Write policy mode. 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.

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.

Direct-Write Policy

When the Direct-Write policy is selected, WebLogic Server writes synchronously to a primary set of files in the location defined by the Directory attribute of the file store configuration using a native I/O wlfileio driver. This policy typically performs slower than the Direct-Write-With-Cache policy, but it uses less disk space and may have fewer environmental considerations to manage. The Direct-Write policy is typically faster than the Cache-Flush policy.

Note:

Cache-Flush Policy

When the Cache-Flush policy is selected, WebLogic Server enables the default file write behavior of the operating system and storage device, which typically includes caching and scheduling file writes, but forces a flush of the cache to disk before completing a transaction. Transactions cannot complete until all of their writes have been flushed down to disk. This policy is reliable and scales well as the number of simultaneous users increases. It is transactionally safe, but tends to provide lower runtime performance than the direct-write policies in typical use cases, except in those cases with large numbers of simultaneous producers or consumers.

Disabled Policy

When the Disabled policy is selected, WebLogic Server relies on the default file write behavior of the operating system and storage device. In most cases, file writes are cached in memory and are scheduled for writing instead of being directly written to disk. The Disabled policy generally improves file store performance, often quite dramatically, but at the expense of possibly losing sent messages or generating duplicate received messages (even if messages are transactional) in the event of an operating system crash or a hardware failure. This is because transactions are complete as soon as their writes are cached in memory, instead of waiting for the writes to successfully reach the disk. Simply shutting down an operating system or killing a WebLogic Server process does not generate these failures, as an OS flushes all outstanding writes under these circumstances during a normal shutdown. Instead, these failures can be emulated by abruptly shutting the power off to a busy server.

Creating a JDBC Store

The following sections provide an example of a JDBC store, and information about creating a database table for a JDBC store, either using existing DDL or It also includes instruction on enabling Oracle blob record columns in a DDL file.

To create a JDBC store, you can directly modify the default JDBCStoreMBean parameters. For instructions on using the Administration Console to create a JDBC store, see "Create JDBC Stores" in the Oracle WebLogic Server Administration Console Help.

For configuration guidelines on using prefixes with JDBC stores and recommended JDBC data source settings, see Guidelines for Configuring a JDBC Store.

Main Steps for Configuring a JDBC Store

The main steps for creating a JDBC store are as follows:

Create a JDBC data source or multi data source to interface with the JDBC store.
Create a JDBC store and associate it with the JDBC data source or multi data source.
It is highly recommended that you configure the Prefix option to a unique value for each configured JDBC store table.
Associate the JDBC store with the subsystem(s) that will be using it, such as:
- For JMS servers, select the JDBC store on the General Configuration page.
- For Store-and-Forward agents, select the JDBC store on the General Configuration page.
- For a Path Service, select the custom file store on the General Configuration page.

Example of a JDBC Store

Here's an example of how a JDBC store may look in the configuration file, using the JDBC data source MyDataSource, and with a logical name specified:

<jdbc-store>
  <name>SampleJDBCStore</name>
  <target>yourserver</target>
  <data-source>MyDataSource</data-source>
  <logical-name>Baz</logical-name>
</jdbc-store>

Table 6-3 describes the JDBC store configuration parameters that can be modified.

Table 6-3 JDBC Store Configuration Option

Option	Required	What It Does
Name	Yes	The name of the JDBC store, which must be unique across all stores in the domain.
Targets	Yes	The server instance or migratable target where a JDBC store is targeted. Multiple subsystems can share the same JDBC store, as long as they are all targeted to the same server instance or migratable target. Note: When using migratable targets for JMS services, you must target the JDBC store to the same migratable target used by the JMS service. See "Service Migration" in Using Clusters for Oracle WebLogic Server.
Data Source	Yes	The JDBC data source or multi data source used by this JDBC store to access the store's database table (`WLStore`). This data source or multi- data source must be targeted to the same server instance as the JDBC store. Note: You cannot specify a JDBC data source that is configured to support global (XA) transactions. Therefore, the specified JDBC data source must use a non-XA JDBC driver. In addition, you cannot enable Logging Last Resource or Emulate Two-Phase Commit in the data source. This limitation does not remove the XA capabilities of layered subsystems that use JDBC stores. For example, WebLogic JMS is fully XA-capable regardless of whether it uses a file store or any JDBC store.
Prefix Name	No	The prefix for the JDBC store's table is generally entered in the following format: `[[[catalog.]schema.]prefix]` When using multiple JDBC stores, it is required to set this option to a unique value for each configured JDBC store. When no prefix is specified, the JDBC store table name is simply `WLStore` and the database implicitly determines the schema according the current user of the JDBC connection. Also, two JDBC stores cannot share the same database table. For more information, see Using Prefixes with a JDBC Store. Modifying an existing JDBC store's prefix does not necessarily require a server restart, as described in Modifying Custom Persistent Store Parameters.
Logical Name	No	Optionally used with WebLogic Server subsystems, like EJBs, when deploying a module to an entire cluster, but also require a different physical store on each server instance in the cluster. In such a configuration, each physical store would have its own name, but all the persistent stores would share the same logical name.
Create Table from DDL File	No	Optionally used with supported DDL (data definition language) files to create the JDBC store's database table (`WLStore`). This option is ignored when the JDBC store's database table already exists. For more information, see Creating a JDBC Store Table Using Default and Custom DDL Files.

For instructions on configuring a JDBC store using the Administration Console, see "Create JDBC Stores" in the Oracle WebLogic Server Administration Console Help.]

Supported JDBC Drivers

When using a JDBC store, the backing database can be any database that is accessible through a JDBC driver. WebLogic Server detects some drivers for supported databases.

For each of these databases, there are corresponding DDL (data definition language) files within the MW_HOME\modules\com.bea.core.store.jdbc_1.0.0.0.jar file, in the weblogic/store/io/jdbc/ddl directory, where MW_HOME is the top-level installation directory of your WebLogic Server installation.

Table 6-4 Supported JDBC Drivers and Corresponding DDL Files

Database	DDL Files
IBM DB2	db2.ddl db2v6.ddl
Informix	informix.ddl
Microsoft SQL (MSSQL) Server	mssql.ddl
MySQL	mysql.ddl
Oracle	oracle.ddl oracle_blob.ddl
Sybase	sysbase.ddl

The DDL files are actually text files containing the SQL commands (terminated by semicolons) that create the JDBC store's database table (WLStore). Therefore, if you are using a database that is not included in this list, you can copy and edit any one of the existing DDL files to suit your specific database, as described in Creating a JDBC Store Table Using a Custom DDL File.

Creating a JDBC Store Table Using Default and Custom DDL Files

The JDBC Store Configuration page provides an optional Create Table from DDL File option, through which you can access a pre-configured DDL file that is used to create the JDBC store's backing table (WLStore). This option is ignored when the JDBC store's backing table already exists. It is mainly used to specify a custom DDL file created for an unsupported database, or when upgrading JMS JDBC store tables from a prior release to a current JDBC Store table.

If a DDL file name is not specified in the Create Table from DDL File field, and the JDBC store detects that its backing table does not already exist, the JDBC store automatically creates the table by executing a pre-configured DDL file that is specific to the database vendor (see Supported JDBC Drivers).

If a DDL file name is specified in the Create Table from DDL File field, and the JDBC store detects that its backing table does not already exist, the JDBC store searches for the specified DDL file in the file path first, and then, if not found, searches for the DDL file in the CLASSPATH. Once found, the SQL within the DDL file is executed to create the JDBC store's backing table. If the configured file is not found and the table doesn't already exist, the JDBC store will fail to boot.

Creating a JDBC Store Table Using a Custom DDL File

To use a different database from those listed in Supported JDBC Drivers, you can copy and edit any one of the existing DDL template files to suit your specific database.

Use the JAR utility supplied with the JDK to extract the DDL files to the /weblogic/store/io/jdbc/ddl directory using the following command:
```
jar xf com.bea.core.store.jdbc_1.0.0.0.jar /weblogic/store/io/jdbc/ddl
```
Note:
If you omit the weblogic/store/io/jdbc/ddl parameter, the entire jar file is extracted.
Edit the DDL file for your database. An SQL command can span several lines and is terminated with a semicolon (;). Lines beginning with pound signs (#) are comments.
Save your changes and rename the new DDL appropriately (for example, mydatabase.ddl)
Create a JDBC store, as explained in "Create JDBC Stores" in the Oracle WebLogic Server Administration Console Help.
Use the Create Table from DDL File option on the General Configuration page to specify your custom DDL file (for example, /mydatabase.ddl).

Note:
On Windows systems, for full path names always include the drive letter.

Enabling Oracle BLOB Record Columns

For Oracle databases, you can use the oracle_blob.ddl file to create a JDBC store table with a BLOB record column type rather than the default LONG RAW record column type. The oracle_blob.ddl file is pre-configured and supplied in the WebLogic CLASSPATH, as described in Supported JDBC Drivers.

To use the Oracle BLOB DDL with a JDBC store:

Shut down the server instance that uses the JDBC store.
Delete the current JDBC table, as explained in Managing JDBC Store Tables.
Reboot the server instance.
Create a new JDBC store, as explained in "Create JDBC Stores" in the Oracle WebLogic Server Administration Console Help.
In the Create Table from DDL File field on the General Configuration page, enter the location of the oracle_blob.ddl file, as follows: /oracle_blob.ddl
Click Finish to create the JDBC store's backing table.

If you need to preserve data already in a Oracle LONG RAW column, but still want to switch the column to BLOB, do not use this method. Instead, consult the Oracle documentation for the SQL ALTER TABLE command.

Managing JDBC Store Tables

The JDBC utils.Schema utility allows you to regenerate a new JDBC store database table (WLStore) by deleting the existing version. Running this utility is usually not necessary, since WebLogic Server automatically creates this table for you. However, if your existing JDBC store database table somehow becomes corrupted, you can delete it using the utils.Schema utility.

The utils.Schema utility is a Java program that takes command-line arguments to specify the following:

JDBC driver
Database connection information
Name of a file containing the SQL Data Definition Language (DDL) commands that create the database table

Using the utils.Schema Utility to Delete a JDBC Store Table

Enter the utils.Schema command, as follows:

$ java utils.Schema url JDBC_driver [options] DDL_file

Note:

To execute utils.Schema, your CLASSPATH must contain the weblogic.jar file.

Table 6-5 lists the utils.Schema command-line arguments.

Table 6-5 Command-line arguments for utils.Schema

Argument	Description
url	Database connection URL. This value must be a colon-separated URL as defined by the JDBC specification.
JDBC_driver	Full package name of the JDBC Driver class.
options	Optional command options. If required by the database, you can specify: The user name and password as follows: -u <username> -p <password> The Domain Name Server (DNS) name of the JDBC database server as follows: -s <dbserver> You can also specify the `-verbose` option, which causes `utils.Schema` to echo SQL commands as they are executed.
DDL_file	The full pathname of the DDL text file containing the SQL commands that you want to execute. For more information, see Supported JDBC Drivers.

For example, the following command deletes a JDBC table named MYWLStore in an Oracle server named DEMO, with the user name user1 and password foobar:

$ echo "drop MYWLStore;" > drop.ddl

$ java utils.Schema 
jdbc:weblogic:oracle:DEMO \
weblogic.jdbc.oci.Driver -u user1 -p foobar -verbose \
drop.ddl

Guidelines for Configuring a JDBC Store

The following sections provide guidelines for using JDBC store prefixes, recommended WebLogic JDBC data source settings for JDBC stores, and handling JMS transactions with JDBC stores.

Using Prefixes with a JDBC Store

The JDBC store database contains a database table, named WLStore, that is generated automatically and is used internally by WebLogic Server. The JDBC store provides an optional Prefix Name parameter, which can be used to provide more precise access to the database table.

It is always a best practice to configure a prefix for the JDBC WLStore table name, especially when:

The database requires fully-qualified names. (You should verify this with your database administrator.)
There is more than one JDBC store instance sharing a database, since no two JDBC stores can share the same table.
There are many tables in the database. Setting the prefix reduces the number of tables the JDBC store must search through to find its table during boot.

JDBC Store Table Rules

To avoid potential data loss, follow these rules:

Each JDBC store table name must be unique.
If multiple JDBC stores share a table, the behavior is undefined and data loss is likely.
There is no procedure for combining two database tables into a single table.

Prefix Name Format Guidelines

For most databases, the Prefix Name option for the JDBC store's backing database table should be set in the following format for each configured JDBC store, which will result in a valid table name when prepended to the JDBC store table name:

[[[catalog.]schema.]prefix]

Note that each period in the [[[catalog.]schema.]prefix] format is significant. Generally, catalog identifies the set of system tables being referenced by the DBMS, and schema generally corresponds to ID of the table owner (username). When no prefix is specified, the JDBC store table name is simply WLStore and the database implicitly determines the schema according the current user of the JDBC connection.

For example, in a production database, the database administrator could maintain a unique table for the Sales department, as follows:

[[[Production.]JMSAdmin.]Sales]

The resulting table will be created in the Production catalog, under the JMSAdmin schema, and will be named SalesWLStore.

For some DBMS vendors, such as Oracle, there is no catalog to set or choose, so the format simplifies to [[schema.]prefix]. For more information, refer to your DBMS documentation for instructions on fully-qualified table names, but note that the syntax specified by the DBMS may differ from the format required for this option.

Caution:

If the Prefix Name setting is changed, but the WLStore database table already exists in the database, take care to preserve existing table data. In this case, the existing database table must be renamed by a database administrator to match the new configured table name.

Recommended JDBC Data Source Settings for JDBC Stores

The following settings are recommended when you use a JDBC data source or multi data source for JDBC stores.

Automatic Reconnection to Failed Databases

WebLogic Server provides robust JDBC data sources that can automatically reconnect to failed databases after they come back online, without requiring you to restart WebLogic Server. To take advantage of this capability, and make your use of JDBC stores more robust, configure the following options on the JDBC data source associated with the JDBC store:

TestConnectionsOnReserve="true"
TestTableName="SYSTABLES"
ConnectionCreationRetryFrequencySeconds="600"

For more information about JDBC default Test Table Names, see "Connection Testing Options for a Data Source" in the Configuring and Managing JDBC for Oracle WebLogic Server. For more information about setting the number of database reconnection attempts, see the "Enabling Connection Creation Retries" section in Configuring and Managing JDBC for Oracle WebLogic Server.

Required Setting for Oracle DB2 Type 4 JDBC Drivers

For data sources used as a JDBC store that use the Oracle Type 4 JDBC driver for DB2, the BatchPerformanceWorkaround property must be set to "true" due to internal JMS batching requirements.

For more information, see the "Performance Considerations" in Type 4 JDBC Drivers for Oracle WebLogic Server.

Handling JMS Transactions with JDBC Stores

You cannot configure a JDBC store to use a JDBC data source that is configured to support global (XA) transactions. The JDBC store must use a JDBC data source that uses a non-XA JDBC driver. In addition, you cannot enable Logging Last Resource or Emulate Two-Phase Commit in the data source. This limitation does not remove the XA capabilities of layered subsystems that use JDBC stores. For example, WebLogic JMS is fully XA-capable regardless of whether it uses a file store or any JDBC store.

Because the JDBC store implements the XAResource interface, it acts as it's own resource manager and handles the transactions above the JDBC driver level. That is, the store itself implements the XAResource and handles the transactions without depending on the database (even when the messages are stored in the database).

This means that whenever you are using a JDBC store and a database (even if it is the same database where the JMS messages are stored), then it is two-phase commit transaction.

For more information about using JMS transactions with a JDBC store, see "Using Transactions with WebLogic JMS" in Programming JMS for Oracle WebLogic Server.

From a performance perspective, you may also boost your performance as follows:

Ensure that the JDBC data source used for the database work exists on the same server instance as the JMS destination—the transaction will still be two-phase, but it will be handled with less network overhead.
Use file stores rather than JDBC stores.
Configure multiple services to share the same store if they will commonly be invoked within the same transaction.
If an application directly performs database operations in addition to invoking store services (such as JMS) within the same transaction, consider using a JDBC data source with Logging Last Resource (LLR) enabled for the database operations.

With the LLR optimization, the transaction will follow the two-phase commit protocol, but the database operations will be handled in a single local transaction, which may improve overall transaction performance. For more information on using the LLR optimization, see "Understanding the Logging Last Resource Transaction Option" in Configuring and Managing JDBC for Oracle WebLogic Server.

Monitoring a Persistent Store

You can monitor statistics for each existing persistent store and for each open store connection.

Monitoring Stores

Each persistent store is represented at run time by an instance of the PersistentStoreRuntimeMBean, which provides the following options.

Table 6-6 Persistent Store Run-time Options

Option	What It Does
CreateCount	Number of create requests issued to this persistent store.
ReadCount	Number of read requests issued to this persistent store.
UpdateCount	Number of update requests issued by this persistent store.
DeleteCount	Number of delete requests issued by this persistent store.
ObjectCount	Number of objects contained in the persistent store.
Connections	Number of active connections in the persistent store.
PhysicalWriteCount	Number of times the persistent store flushes its data to durable storage.

Monitoring Store Connections

For each open persistent store connection, the persistent store also registers a PersistentStoreConnectionRuntimemMBean, which provides the following options.

Table 6-7 Persistent Store Connection Runtime Options

Option	What It Does
CreateCount	Number of create requests issued to this connection.
ReadCount	Number of read requests issued to this connection.
UpdateCount	Number of update requests issued by this connection.
DeleteCount	Number of delete requests issued by this connection.
ObjectCount	Number of objects contained in the connection.

Table 6-8 defines most of the run-time prefix names of the WebLogic services and subsystems that can create a connection to the persistent store.

Table 6-8 Persistent Store Run-Time Prefix Names

Subsystem/Service	Run-Time Prefix Name
Deployment	weblogic.deploy.internal where `internal` is the name of the deployment connection
Diagnostic Service	weblogic.diagnostics.internal where `internal` is the logical name of the diagnostic archive connection
EJB Timer Services	weblogic.ejb.timer.internal where `internal` uniquely identifies EJB deployments in a server instance
JMS Service	JMS server: weblogic.messaging.jmsServer.internal where `internal` is the name of the JMS server connection JMS durable subscriber: weblogic.messaging.jmsServer.durablesubs.internal where `internal` is the name of the durable subscriber connection
JTA Transaction Log (TLOG)	weblogic.transaction.internal where `internal` is the name of the TLOG connection
Path Service	weblogic.messaging.PathService.internal where `internal` is the name of the path service connection
SAF Service	SAF agent weblogic.messaging.SAFAgent@server1.internal where `internal` is the name of the SAF agent's connection SAF durable subscriber: weblogic.messaging.SAFAgent@server1.durablesubs.internal where `internal` is the name of the durable subscriber connection
Web Services	weblogic.wsee.server.store.internal where `internal` is the name of the Web Service's connection

Administering a Persistent Store

The WebLogic Store administration utility enables administrators to troubleshoot a WebLogic persistent store. The store utility operates only on a store that is not currently opened by a running server instance. This utility can be run from a Java command line or from WebLogic Scripting Tool (WLST), as described in Store Administration Using a Java Command Line and Store Administration Using WLST.

The most common uses-cases for store administration are for compacting a file store to reduce its size and for dumping the contents of a file store of JDBC store to an XML file for troubleshooting purposes. Examples of these use cases are provided later in this section.

Table 6-9 defines the available store administration commands for Java and WLST.

Table 6-9 Persistent Store Administration Options

Java Command	WLST Method	What It Does
help	helpstore	Displays available commands, usage, and examples.
compact	compactstore	Compacts and defragments the space occupied by a file store. This command only works offline and does not work for JDBC stores. Note: Compacting a file store is usually not necessary if you know that file store will likely grow to the current size again. File stores automatically re-use space freed by deleted records and expand only when there is insufficient internal space for new records. Also, file stores do not normally become fragmented as most persistent records are short-lived.
openfile	openfilestore	Opens an existing file store for further operations. If a file store does not exist, a new one is created in an open state using the `-create` parameter.
openjdbc	openjdbcstore	Opens an existing JDBC store for further operations. If a JDBC store does not exist, a new one is created in an open state
dump	dumpstore	Dumps store or connection contents in a human-readable format to user-specified XML file. The XML file format is the same format used by the diagnostic image of the persistent store.
list	liststore	Lists store names, open stores, or connections in a store.
n/a	getstoreconns	Returns a list of connections in the specified store (for script access)
n/a	getopenstores	Returns a list of opened stores (for script access).
opts	n/a	Lists invocation options for the store administration tool.
verbose	n/a	Controls display of additional information, such as stack traces.
close	closestore	Closes a previously opened store.
quit	exit	Ends the store administration session.

A persistent store can be backed by the file system (file store) or by a JDBC-capable database (JDBC store). Except for the openfile/openfilestore() and openjdbc/openjdbcstore() options, there is no difference in the options to operate on these two different types of stores.

Most commands and methods work in terms of store names, while others also work in terms of connection names. Store connections are logical groups of records within persistent stores. For example, the JMS and JTA subsystems persist their respective records in different connections in the same store.

Store Administration Using a Java Command Line

To open the persistent store administration utility from a Java command line, type the following:

> java weblogic.store.Admin
> storeadmin->

Accessing Store Administration Help

Type help for detailed descriptions on available store administration commands, as well as examples of typical command usage. For example, the following comprehensive help is provided for the list command, which lists store names, open stores, or connections in a store.

storeadmin->help list
  Command:
    list
  Description:
    lists store names, open stores, or connections in a store
  Usage:
    list [-store storename|-dir dir]
  Examples:
    list #lists all opened stores by storename
    list -store store1 #lists all connections in store1
    list -dir dir1 #lists all storenames found in dir1

Dumping the Contents of a File Store

Here's an example of using a series of store administration commands to ultimately export the contents of a file store named myfilestore into a human-readable XML file format in a temporary directory. This does not include store connection names or the actual record contents, which require the optional -conn and -deep parameters.

> storeadmin-> list -dir .
> storeadmin-> openfile -store myfilestore -dir .
> storeadmin-> dump -store myfilestore -out d:\tmp\filestore1-out
> storeadmin-> close -store myfilestore

The list command shows all the store names in the current directory. The openfile and openjdbc commands must be used to open and/or create a file or JDBC store first before calling certain administration functions, like dump and list (only when listing open stores). After administering an open store, you must close it using the close command.

Compacting a File Store

Here is an example of using the compact command to compact the space occupied by a file store in the mystores directory.

> storeadmin->compact -dir c:\mystores -tempdir c:\tmp

Since the compact command can only be used on an unopened file store, none of the stores that have files in the source -dir directory should be open. Also, the temporary -tempdir directory should have at least enough extra space as the source directory and should also not be under the source directory. When compact successfully completes, the newly compacted store files will be in the mystores directory. In addition, a new, uniquely-named directory will be created under tmp containing the original uncompacted store files.

Store Administration Using WLST

The WLST interface has a couple of additional methods (compared to the Java command line) such as getopenstores and getstoreconns, that return relevant Java objects and can be used for scripting in WLST.

Accessing Store Administration Help

To access the persistent store administration utility from WLST, type the following command:

> java weblogic.WLST

Type helpstore() for detailed descriptions on available store administration commands, as well as examples of typical command usage. For example, the following help is provided for the list command, which lists store names, open stores, or connections in a store.

> wls:/offline> helpstore(liststore)
  lists storenames, opened stores, or connections (for interactive access)
  Parameters store and dir cannot both be specified concurrently.

  Usage: liststore(store='null',dir='null')

  @param store [optional] a previously opened JDBC or File store's name.
      If store is specified, all connections in the store are listed.
  @param dir [optional] directory for which to list available store names
      If dir is specified, all store names in the directory are listed.

  If neither store nor dir are specified, all open store names are listed.
  @return 1 on success, 0 on failure

Note that the parameters with an equal sign "=" are optional. For example, the compactstore method can be invoked as either compactstore(dir='storename', tempdir='/tmp') or compactstore(store='storename'), where tempdir takes the default value. Default values for optional parameters are listed in the command-specific help.

Dumping the Contents of a JDBC Store Using WLST

Here is an example of using the dumpstore method (store, outfile, conn='null', deep='false') to export the contents of a JDBC store named myJDBCStore in a human-readable XML file format out to a file named mystoredump-out.xml. This does not include store connection names or the actual record contents, which require the optional conn and deep parameters.

> wls:/offline>
  (openjdbcstore('myJDBCStore', 'oracle.jdbc.OracleDriver',
  'jdbc:oracle:thin:@test2k31:1521:test120a', './wlstoreadmin-dump.props',
  'jmstest', 'jmstest', '', 'jdbcstoreprefix')
  dumpstore('myJDBCStore', 'mystoredump-out')
  closestore('myJDBCStore')

The openjdbcstore and openfilestore methods must be used to open and/or create a store first before calling certain administration functions, like dumpstore and liststore (only when listing open stores). After administering an open store, you must close it using the closestore method.

Compacting a File Store Using WLST

Here is an example of a WLST script that uses the compactstore method (dir,tempdir='null') to compact the space occupied by a file store files in the mystores directory.

> wls:/offline> compactstore('c:\mystores','c:\tmpmystore.dir')

Since the compactstore() method can only be used on unopened file stores, none of the stores that have files in the source 'dir' directory should be open. Also, the temporary 'tempdir' directory should have at least enough extra space as the source directory and should also not be under the source directory. When compact successfully completes, the newly compacted store files will be in the mystores directory. In addition, a new, uniquely-named directory will be created under tmpmystore containing the original uncompacted store files.

Limitations of the Persistent Store

The following limitations apply to the persistent store:

A persistent file store should not be opened simultaneously by two server instances; otherwise, there is no guarantee that the data in the file will not be corrupted. If possible, the persistent store will attempt to return an error in this case, but it will not be possible to detect this condition in every case. It is the responsibility of the administrator to ensure that the persistent store is being used in an environment in which multiple servers will not try to access the same store at the same time. (Two file stores are considered the "same store" if they have the same name and the same directory.)
Two JDBC stores must not share the same database table, because this will result in data corruption.
A persistent store may not survive arbitrary corruption. If the disk file is overwritten with arbitrary data, then the results are undefined. The store may return inconsistent data in this case, or even fail to recover at all.
A file store may return exceptions when its disk is full. However, it will resume normal operation by no longer throwing an exception when disk space has been made available. Also, the data in the persistent store must remain intact as described in the previous points.