Skip Headers
Oracle® Database Lite Troubleshooting and Tuning Guide
10g (10.3.0)

Part Number B28927-01
Go to Documentation Home
Home
Go to Book List
Book List
Go to Table of Contents
Contents
Go to Index
Index
Go to Feedback page
Contact Us

Go to previous page
Previous
Go to next page
Next
View PDF

2 Troubleshooting

This document contains frequently asked questions for troubleshooting the Mobile Server. Topics include:

2.1 Troubleshooting Synchronization

The following sections describe how to troubleshoot the synchronization process or what to do in the event of certain synchronization scenarios:

2.1.1 Synchronization Errors and Conflicts

Consult the following sections for details on how to resolve any synchronization errors or conflicts:

2.1.1.1 General Synchronization Errors and Conflicts

With the Mobile Server, you can have the following errors when synchronizing: nullity violations, foreign key constraint violations, or the client updates a row at the same time that the server deletes it.

The Mobile Server does not automatically resolve synchronization errors. Instead, the Mobile Server rolls back the corresponding transactions, and moves the transaction operations into the Mobile Server error queue. It is up to the administrator to view the error queue and determine if the correct action occurred. If not, the administrator must correct and re-execute the transaction. If it did execute correctly, then purge the transaction from the error queue.

A Mobile Server synchronization conflict occurs if:

  • Nullity violations.

  • Foreign key constraint violations.

  • The client and the server update the same row.

  • The client and server create rows with the same primary key values.

  • The client deletes the same row that the server updates.

  • The client updates a row at the same time that the server deletes it.

See Section 3.11, "Resolving Conflict Resolution with Winning Rules" in the Oracle Database Lite Developer's Guide for more information on conflict resolution techniques.

2.1.1.2 Synchronization Error if Client Device Clock is Inaccurate

The client device clock must be accurate within the timezone set on the device before attempting to synchronize. An inaccurate time may result in the following exception during synchronization: CNS: 9026 "Wrong username or password. Please enter correct value and reSync."

2.1.2 Problems When Synchronizing Large Number of Rows

When you synchronize a large number of rows, you may want to set the AUTO_COMMIT_COUNT parameter in the POLITE.INI file to a smaller number. The smaller the number is, the more often a commit occurs. If you do not set the AUTO_COMMIT_COUNT parameter to a smaller number, you may receive an OutOfMemory error.

See Section G.3.2.5, "AUTO_COMMIT_COUNT" in the Oracle Database Lite Administration and Deployment Guide for information on this parameter.

2.1.3 First Synchronization Causes Browser to Timeout

The duration of the first synchronization process, between the client and the server may take a very long time (For example, upwards of 45 minutes), causing the Microsoft Internet Explorer browser to time out.

The solution is available only for the Microsoft Internet Explorer. For the Mobile Client for Web-to-Go, change the ReceiveTimeout value for a particular registry key on Windows 32. The following paragraphs provide the location of this parameter and specifies how to change its value.

  1. If you want to change the ReceiveTimeout value (that is, the number of milliseconds that the browser will wait to receive the data from the server), uncomment the following two lines in the REGISTRY section of the file setup.ini. This file is downloaded to the client from the server when the Mobile Client for Web-to-Go is first installed on the client machine.

    #KEY: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\       Internet Settings#VALUEDWORD: ReceiveTimeout = 40000000
    
    
  2. To uncomment the two lines, remove the hash marks in front of the KEY and VALUEDWORD statements and then change the ReceiveTimeout value to the desired value in milliseconds. In the example given below, the timeout value is 40000 seconds.

    wsh -o mobileadmin/manager@webtogo.worldcd setupedit setup.ini
    
    
  3. When you modify the file setup.ini in the Mobile Server Repository, the next time that the file is downloaded to the Mobile Client, these two lines will be uncommented.

2.1.4 Situations Where the Client is Out of Sync that Triggers a Complete Refresh

When a client is out of sync with the server, any outstanding uploaded transaction from the client is placed in the error queue and a complete refresh is triggered to re-initialize the client data with what is currently on the server.

The following are a list of the situations—ordered from most to least likely—that can trigger a complete refresh for the client:

  • Dropping and then republishing the application.

  • Synchronizing by the same Mobile user from multiple devices on the same platform or from different platforms when the publications are not platform-specific.

  • Receiving unexpected server apply phase conditions—such as constraint violations, unresolved conflicts, other database exceptions.

  • Modifying the application—such as changing subsetting parameters, or adding or altering publication items.

  • Requesting a force refresh from either the server admin or client.

  • Two separate applications using the same backend store.

  • Unexpected client apply conditions—such as deleting, moving or restoring the Oracle Lite database, database corruption, memory corruption, and other general system failures.

  • Loss of transaction integrity between server and client. The server fails post processing after completing a download and disconnecting from the client.

  • Data transport corruptions.

2.1.5 The "Inconsistent Datatypes" SQLException Received If Order is Not Correct in Query

If you are creating a fast refresh publication item on a table with a composite primary key, the snapshot query should list the primary key columns in the order that they are present in the table definition. This automatically happens during the column selection when MDW is used or when a SELECT * query is used. Note that the order of the primary key columns in the table definition may be different from those in the primary key constraint definition.

The following example demonstrates what is valid or invalid given the table definition for TAB1:

CREATE TABLE TAB1(
 ID1 NUMBER(10) NOT NULL,
 ID2 NUMBER NOT NULL,
 COL1 VARCHAR2(200),
 COL2 VARCHAR2(200),
 ID3 NUMBER(4) NOT NULL);
ALTER TABLE TAB1 ADD CONSTRAINT TAB1_PK PRIMARY KEY (ID3, ID2, ID1);

The following are valid snapshot queries:

SELECT * FROM TAB1
SELECT ID1,ID2,ID3,COL1,COL2 FROM TAB1
SELECT ID1,ID2,COL1,COL2,ID3 FROM TAB1

The following are invalid snapshot queries:

SELECT ID3,ID2,ID1,COL1,COL2 FROM TAB1
SELECT ID3,ID2,COL1,COL2 ID1 FROM TAB1

Define the table columns where the primary key columns appear before other columns. The order of the primary key columns in the table definition order must match the constraint definition in the snapshot query.

2.1.6 MGP Compose Postponed Due to Transaction in the In-Queue

If the user synchronized and uploaded some more changes after the last apply cycle for a particular user; by default, the MGP must first apply thse changes before it can compose. If this keeps happening, the compose could be postponed beyond what you would like. By default, the MGP tries to avoid a compose phase postponed due to a transaction in the in-queue by performing an apply for any unprocessed in-queue data before doing a new compose. However, if the MGP compose is postponed due to a transaction in the in-queue, you can modify the following parameters to avoid the error:

  • SKIP_INQ_CHK_BFR_COMPOSE: By default, this parameter is set to NO. Setting this parameter to YES, then a compose is performed for a client even if there is unprocessed data in the in-queue.

  • DO_APPLY_BFR_COMPOSE: By default, this parameter is set to YES. If set to YES, the unprocessed data in the in-queue is applied before a client compose. This parameter takes effect only if SKIP_INQ_CHK_BFR_COMPOSE is set to NO.

For most situations, preserving the default values for these two parameters avoids the occurrence of the MGP Compose postponed error.

2.1.7 Avoiding the Server Busy Warning

The Server Busy warning can be thrown for one of the following reasons:

  • When the MGP is processing apply/compose for that user.—To avoid MGP contention with sychronization, MGP should be scheduled to run when few clients are synchronizing. Alternatively, you could use queue-based synchronization, which does not use the MGP at all; thus, avoiding MGP contention with synchronizaiton.

  • If a previous synchronization was interrupted for that user and Oracle Database Lite rolls back the transaction—If the Server Busy warning is a result of a long rollback, then Oracle Database recommended tuning steps for rollback operation may reduce the Server Busy state for the client.

2.1.8 Enabling Online Web-to-Go Applications on the Mobile Server Host

When you publish you application, you can immediately initialize a synchronization from the client. However, if you want to use the application on the same host as the Mobile Server, you will receive an error.

The OC4J layer under the Mobile Server does not support auto deployment of the Web application in the Online Mode. If the user wants to access the Web application in the online mode immediately after publishing, then the administrator must restart the Mobile Server.

If you only have the random Web application that you wish to access in this manner, just restart the Mobile Server. However, if you want to have multiple applications to be automatically deployed, you can enable the auto deployment option. This is not recommended as it has an adverse effect on the performance of the Mobile Server.

To enable the auto deployment in the Mobile Server, perform the following:

  1. Open the <J2EE_HOME>\mobileserver\config\server.xml file.

  2. Modify the check-for-updates parameter from adminClientOnly to all.

    Note:

    Modifying this parameter enables the Mobile Server to recognize any newly published applications on the host of the Mobile Server. However, it also degrades performance.
  3. Save the server.xml file.

  4. Restart the Mobile Server.

2.2 Troubleshooting the Mobile Server

The following sections detail how to troubleshoot the Mobile Server and its repository:

2.2.1 Running the Mobile Server With Tracing Enabled

If you experience any difficulty with the Mobile Server running with the application server or the standalone Mobile Server, you can enable tracing in the Mobile Server.

To enable tracing in the Mobile Server, set up your environment as described in Section 3.1, "Enable Tracing on the Mobile Server". To enable tracing on your Mobile Client, follow the instructions in Section 3.2, "Enable Tracing on Mobile Clients".

2.2.2 Troubleshooting an Address Already In Use Error

When you start the Mobile Server, it fails with the following error:

ERROR J2EE RMI0002 Error starting ORMI server
@ 1 port 23,791: Address already in use: JVM_Bind
ERROR java.net.BindException: Address already in
use: JVM_Bind
 

You need to modify the RMI and JMS ports in the rmi.xml and jms.xml file, which are located in the <ORACLE_HOME>\mobile_oc4j\j2ee\mobileserver\config directory. The port numbers may not already be in use by another process.

Normally, this error is caused by installing either of the following:

  • Two standalone Mobile Servers on a single machine

  • A standalone Mobile Server and a Web-to-Go client for OC4J on the same machine

2.2.3 Overwriting OracleAS WEB.XML Causes Connection Failure

When you install OracleAS and Oracle Database Lite; normally, you install the OracleAS first and then Oracle Database Lite. The Oracle Database Lite adds an entry to the web.xml file to define Oracle Database Lite as a Web service. This includes a definition and location of the webtogo.ora file. So, if you have reinstalled OracleAS or corrupted the web.xml file in any way, Oracle Database Lite and OracleAS do not interact as they should.

The best method is to reinstall Oracle Database Lite on top of a fresh OracleAS installation. Otherwise, if you have a backup copy of the web.xml file, you may only need to overwrite the new one with the backed up copy. Verify that everything is the same except for the addition of a web-app definition for webtogo-web.

2.3 Troubleshooting the Mobile Server Repository

The following sections describe how to recover the Mobile Server Repository:

2.3.1 Troubleshooting the Mobile Server Repository with the Mobile Server Repository and Diagnostic Tool (MSRDT)

Customers may modify the Mobile Server repository in the back-end database and, without realizing it, violate some of the rules. We have provided a tool that helps you analyze, validate, and debug the repository.

The Mobile Server Repository Diagnosis tool evaluates the repository and prints out only what is found to be modified or missing. The output generated is best viewed if you set your column width to 80 or if you pipe it into a file, to view it with Word or WordPad.

2.3.1.1 Inspecting Files in the Mobile Server Repository

You can use the Mobile Server shell utility (wsh) to inspect and modify the Mobile Server Repository interactively. Start the Command Prompt and enter the following.

wsh -L system/x@olite-db

OR

wsh -o <adminuser>/<adminuser's password>@o8db

For example, you could enter the following sample codes at the command prompt.

wsh -o administrator/admin@webtogo.worldwsh -L system/x@webtogo

This displays the Mobile Server Repository prompt.

The following table lists commands that are available for inspecting and altering the Mobile Server Repository.

Table 2-1 describes available commands for inspecting and altering the Mobile Server Repository.

Table 2-1 Commands to Inspect and Alter the Mobile Server Repository

Command Definition

dir

Displays a list of files in a directory.

copy

Copies one or more files to another location.

cp

Copies one or more files to another location.

edit

Launches Notepad for editing a file.

del

Deletes one or more files.

rm

Deletes one or more files.

cd

Displays the name or changes the current directory.

md

Creates a directory.

rd

Removes (deletes) a directory. Use the option -s to remove a directory including all subdirectories.

type

Displays the contents of a text file or files.

exit

Quits the command shell.

quit

Quits the command shell.

help

Provides help information for shell commands.

sync

Synchronizes the file system with the database.


2.3.1.2 Use the Mobile Server Repository and Diagnostic Tool to Validate Your Environment and the Repository

You can use the Mobile Server Repository and Diagnostic Tool (MSRDT) to validate your environment and what is in the back-end Mobile Server repository. The following sections describe the validation that occurs:

2.3.1.2.1 Validate the Environment for the Mobile Server

Displays the system configuration environment for the host where the Mobile Server resides, as follows:

  • Web-to-Go version

  • Consolidator version

  • Back-end Oracle database version

  • Definition of the Java library path

  • Definition of the Java CLASSPATH

  • Operating system architecture, type and version

  • Java VM vendor, version, name, home, and info (mode)

  • File encoding used

  • Path separator and file separator used

  • Country, time zone, and user language

  • Lists the Mobile Server administrators

  • Lists the contents/current configuration for the webtogo.ora file

2.3.1.2.2 Validate Integrity of Mobile Server Tables and Data

When Mobile Server and the repository are installed, certain tables, constraints, objects, and so on cannot be modified. This part of the diagnostic tool checks that these requirements are still the same as when installed, which includes the following:

  • Required tables exist

  • All columns within required tables exist

  • Required table attributes exist

  • Required constraints exist or have not been modified

  • Required sequences exist

  • Extra tables have not been added to Mobile Server schemas

  • Web-to-Go system and its application publications exist

  • Application files integrity check: If you have published an application to the server, then check if the folder exists and is not empty. Also, if sharing a repository among multiple Mobile Servers, ensures that the application is published on this Mobile Server, where this tool is executed.

2.3.1.2.3 Validate the Structure and Contents of the Repository

If you are experiencing trouble with your repository, execute this tool to determine if any of the following have occurred:

  • The mapping between primary keys for the map table and corresponding base table must be consistent.

  • Invalid indexes

  • Consistency of the In-Queue schema with the view schema.

  • The records in the in-queue master table have corresponding records in the in-queue detail table.

  • Any DML locked tables or entries in the C$ALL_LOGGED_TABLES.

  • Invalid triggers.

  • Validate that all of the users subscribed to a publication also have all of the corresponding sequences assigned to the same publication.

  • Invalid sequence valu es.

  • Validate that every column in C$ALL_SEQUENCES has its own table, which is named C$WD_<column>.

  • Validate that every window sequence has the same id as a record in the C$ALL_SEQUENCES.

  • Look for any orphaned objects in the repository.

  • Verify that the Mobile Server repository owner is granted with sufficient privileges.

  • Validate the MGP properties: If MGP_SUSPEND(apply suspend) is false, then MGP_RUN must be true.

  • Reports on the most recent jobs and their status.

2.3.1.3 Execute the Repository Diagnostics Tool

The following is the usage and syntax for the Mobile Server repository diagnostics tool—msrdt:

msrdt <options>

Where <options> are the following:

Table 2-2 List of Options for Repository Diagnostic Tool

Tasks Options Description

Validate Repository

-v <username>/<pwd>@<hostname>:<port>:<SID>

Validates the repository and provides error reporting. Performs some error recovery.


2.3.2 Modifying IP Address of Machine Where Mobile Server Repository Exists

During the installation, the machine name or IP address is provided by the user where the repository is created. If the IP address of the machine changes, then perform one of the two options:

  • If the user provided the machine name; then even after the IP change, the machine name will still work.

  • If user provided the IP address—instead of machine name—then after changing the IP address of the repository machine, the user must change the ADMIN_JDBC_URL and THIN_JDBC_URL parameters in the webtogo.ora file on the Mobile Server.

2.4 Troubleshooting the Oracle Lite Databases

The following sections detail how to either work with the client database or modify an existing schema on the back-end Oracle database:

2.4.1 Accessing the Client Database Offline

When you go offline, after being online, and you need to access your client database, use your Mobile user password, not the password manager. It is the password that you enter when you logged in, before going offline.

If you do not use your Mobile user password when you try to access your client database offline, you will receive the following error message.

[POL-5150] access violation

For example, if you log in as JOHN/JOHN on a Windows 32 machine with contains a Mobile Client for Web-to-Go, and JOHN goes offline, the user database created for JOHN on the client machine requires JOHN's password for access.

If you use mSQL to access the user database, start the Command Prompt and enter the following statement.

msql system/john@jdbc:polite:john_todo

In this example, JOHN's password is john, and the DSN name that was created automatically on the client for the user name JOHN is john_todo.

Syntax

The following syntax enables you to access the user database.

msql system/<mobile user's password>@jdbc:polite:<dsn created for the user>

To find the DSN name, use the ODBC Admin tool on your client machine.

2.4.2 Determining Source of Checksum Error Against Database

You can perform diagnostics if you experience database corruption due to file system write errors, I/O errors, or a media device problem. If you receive a POL-3207 error, you may wish to execute the validatedb tool to see if it is a checksum error. Then, setting OLITE_WRITE_VERIFY to TRUE generates error reporting if a checksum error occurs on the device for the Mobile client.

For more information, see Section G.2.15 "OLITE_WRITE_VERIFY" in the Oracle Database Lite Administration and Deployment Guide.

2.5 Troubleshooting JVM Errors

This section focuses on how to debug the following Java errors:

2.5.1 Troubleshooting An Out of Memory Error

The Mobile Server executes within the OC4J container, which in turn runs on a Java virtual machine (JVM). When you are experiencing the OutOfMemory error, then you should have an understanding of JVM memory architecture and OC4J when tuning Mobile Server performance.

The following may cause an OutOfMemory error:

2.5.1.1 JVM Memory Settings

JVMs may have different implementations of memory management and garbage collection schemes. But at a higher level, they all arrange the memory in the following three areas:

This section describes how to modify the allocation of memory to the JVM memory areas.

Note:

Memory should be allocated properly for the three areas. Otherwise, different kinds of OutOfMemory error may surface.
2.5.1.1.1 Java Heap

The Java heap is where Java objects live. It consists of both the young and tenured generations. The amount of Java heap memory that the JVM starts with is designated by the initial heap size option (-Xms) and the maximum heap size option (-Xmx).

If you see from the stack trace that a Java method throws an OutOfMemory error, then you have exhausted your Java heap space.

For example:

java.lang.OutOfMemoryError: Java heap space

The default settings for the Java heap for a SunUNIX JVM is as follows: Xmx:64M Xms:4M. However, the default for the Mobile Server—if you start up the Mobile Server with the runmobileserver.bat executable—is set to Xmx:256M Xms:512M.

The size of the space reserved can be specified with the -Xmx option. The -Xms specifies the space that is immediately committed to the virtual machine. We recommend to allocate ¼ to ½ of the available physical memory to Java Heap. If you set the maximum Java Heap size to be large—such as, 512M—and you still receive this error, then there may be a leak in the Java code.

The following shows the syntax for how to increase the amount of Java heap memory available to the JVM through the -Xms and -Xmx Java switches:

java -Xms<memory_size>m -Xmx<memory_size>m -jar oc4j.jar

The amounts specified should be based on the available resources. At the minimum, you should set both values to at least 256 MB. The following allocates 768M for both the initial and maximum heap sizes. Of course, the amount of memory you allocate depends on what you have available.

java -Xms768m -Xmx768m -jar oc4j.jar 

Note:

Set the Java heap memory size before starting the Mobile Server with the runmobileserver executable.
2.5.1.1.2 Permanent Generation

The permanent generation holds data needed by the JVM that describes objects which do not have an equivalence at the Java language level. For example, permanent generation is where the classes are loaded. It holds objects that describe classes and methods.

If a classloader method or a String intern method throws an OutOfMemory error in the stack trace, then you have run out of permanent generation space.

For example:

java.lang.OutOfMemoryError: PermGen space at
java.lang.ClassLoader.defineClass1(Native Method) at
java.lang.ClassLoader.defineClass(ClassLoader.java:620)

The default for the permanent generation for a Sun UNIX JVM is 64MB. To set a new initial size for the Sun JVM, use the -XX:PermSize option when starting the virtual machine. To set the maximum permanent generation size use the -XX:MaxPermSize option.

2.5.1.1.3 Native Space

The native space is the memory used by native code, which includes JVM native code and application JNI calls. If a native method throws an OutOfMemory error or the JVM crashes with such an error, then you run out of native space.

For example:

java.lang.OutOfMemoryError: requested 14892 bytes. Out of swap space?
java.lang.OutOfMemoryError: unable to create new native thread

The native space is the (Available physical memory) – (Java heap + Permanent generation). There is no way to set the native space, except to decrease the Java heap or permanent space. If you allocate too much memory for the Java heap, then the native code is left with not enough memory and may run out. If you have to increase the native memory, then decrease the -Xmx parameter to a reasonable value to leave enough memory for the native space. If you still get this error, the native code may have a memory leak.

2.5.1.1.4 Setting Java Options for Java Memory

Set the Java options when you start the OC4J container. The following example sets the initial Java heap to 256M, the maximum Java heap to 512M, and the permanent generation memory to 64M:

java –Xms=256m –Xmx=512m -XX:MaxPermSize=64m oc4j.jar

You set the Java options depending on the environment, as follows:

  • The JAVA_OPTIONS parameter in the WEBTOGO.ORA file is used only for client-side settings. This parameter is ignored on the server-side.

  • For the Mobile Server, all modifications for the Java options must be specified on the command-line or in the runmobileserver.bat file.

  • When modifying the Java memory options for OracleAS, modify the JVM settings in the opmn.xml file, which is located in the <IAS_HOME>/opmn/conf directory.

    In the opmn.xml file, search for process-type id="mobileserver" and then modify the java-options parameter under category id="start-parameters", as shown below:

    <process-type id="mobileserver" module-id="OC4J">
     <module-data>
     <category id="start-parameters">
     <data id="java-options" value="-server -Xrs 
       -Djava.security.policy=/j2ee/mobileserver/config/java2.policy 
       -Djava.awt.headless=true"/>
     <data id="oc4j-options" value="-properties"/>
    
    

By default, the MGP executes as a job in the Job Scheduler in the Mobile Server. Thus, the MGP and other Mobile Server components, such as the Sync Server, share the same memory space. This provides efficiency and manageability; however, if the MGP has a memory leak, then the Mobile Server is affected. In this case, perform the following:

  1. Disable the MGP job.

  2. Restart the Mobile Server.

  3. Restart the MGP in a separate JVM with either the mgp.bat or, if using UNIX, the mgp shell script. This JVM is restarted periodically and may hide the memory leak issue.

Note:

Set the Java memory options for the MGP in the mgp.bat file.

With a larger Java heap size, the garbage collector collects less often and consumes less CPU time. Therefore, a larger heap size is desired for better performance. For the Mobile Server, most of the code is Java code; for the Oracle Lite JDBC connection and Java mSync client, most of the code is in native code. So, setting the Java heap size larger, helps the efficiency and performance of the Mobile Server; however, if it is set too high, the JDBC connection and mSync client may have memory issues.

2.5.1.2 Modifying Java Options for Java Memory When Using Oracle AS

If you are using Oracle AS, then set the JVM settings for your Java memory in the opmn.xml file, which is located in the <IAS_HOME>/opmn/conf/ directory. Inside the opmn.xml file, perform the following:

  1. Modify process-type id="mobileserver".

  2. Change java-options under category id="start-parameters".

The following is an example of this modification:

<process-type id="mobileserver" module-id="OC4J">
   <module-data>
      <category id="start-parameters">
          <data id="java-options" value="-server -Xrs 
              -Djava.security.policy=/j2ee/mobileserver/config/java2.policy 
              -Djava.awt.headless=true"/>
           <data id="oc4j-options" value="-properties"/>

2.5.1.3 Why is Memory Not Released?

You may expect Mobile Server to release the free memory back to operating system after it has finished its work. However, the Mobile Server holds a large amount of memory even when it is idle. This may not be an indication of memory leak; instead, it may be for one or more of the following reasons:

  • If you set the -Xms option to a large number—such as, 1024M—then you should expect the Mobile Server process to use at least 1024M until the process is killed.

  • For performance reasons, the Mobile Server caches metadata in Java heap memory.

  • The garbage collector may not collect the objects right way when they are no longer referenced. In addition, the garbage collector keeps a large amount of free memory in the Java heap for future allocations, instead of returning them to the operating system. You can use Java options to adjust the free memory size; instead, view the Mobile Server total runtime Java heap size and free heap size in the Mobile Manager at Mobile Manager->Data Synchronization->Host.

2.5.1.4 Thread Memory Consumption and Concurrency

The Java heap and permanent generation together are called managed heap, since the garbage collector manages them. The native space can be divided into native heap and thread stack space. Each thread consumes memory, as follows:

  • Each thread created consumes about 1MB stack space, although it is JVM dependent. Take this memory into consideration if you execute multiple threads. For example, on a 32-bit x86 system, the (managed heap + native heap + thread stack size * number of threads) could not exceed 2 GB. On any system, ensure that the total JVM memory is less than the available physical memory size.

  • Each thread allocates additional Java and native heap memory as it executes.

  • There is an overhead associated with multi-threading. Therefore, be careful when executing too many concurrent threads. If concurrency is set to larger than 20, then you are more likely decreasing the Mobile Server throughput—instead of increasing it.

You can control the concurrency of Mobile Server; that is, the OC4J layer and the synchronization layer, as follows:

2.5.1.4.1 Configure the Number of HTTP Sessions

Set the OC4J max-http-connections parameter in the server.xml file, which is located at <ORACLE_HOME>/j2ee/mobileaserver/config/. This OC4J parameter affects all HTTP sessions, which includes Mobile Manager Web requests.

For example, the following sets the max-http-connections parameter to 10:

<application-server … … >
   <max-http-connections max-connections-queue-timeout="180" 
      socket-backlog="50" value="10"> 
   </max-http-connections>
…
</application-server>

The following table describes the attributes of the max-http-connections parameter:

Table 2-3

Attribute Description

max-connections-queue-timeout

Specifies the number of seconds to wait for an available connection. The connection may be waiting if the maximum connections has been reached before returning either "server busy" or "redirect" messages.

Default value: 10 seconds

socket-backlog

Specifies the number of connections that can be queued up before denying connections at the socket level. Default: 30.

value

Specifies the maximum number of connections. Default: 100000.


2.5.1.4.2 Configure the Synchronization Session Thread Concurrency and MGP Thread Maximum

To control the synchronization session thread concurrency, set the Consolidator parameters MAX_CONCURRENT and MAX_CONCURRENT_TIMEOUT. To control the number of threads spawned within the MGP process, set the Consolidator parameter MAX_THREADS. See Section A.6, "CONSOLIDATOR" in the Oracle Database Lite Administration and Deployment Guide for more information on these parameters.

2.5.2 Troubleshooting an IllegalArgumentException

If you receive the java.lang.IllegalArgumentException: Signal already used by VM:SIGINT exception and you are using Branch Office, then you are using a JRE version previous to version 1.4.2. Update to JRE version 1.4.2 or later.

2.6 Troubleshooting Security

The following section describes how to troubleshoot security issues:

2.6.1 SSL Certificate Rejection for Client Authentication

If you are using a reverse proxy and have configured SSL between the client and the reverse proxy, you may receive the following error:

A certificate is required to complete client authentication.

For all clients, except Web-to-Go clients, you can only use SSL authentication with a signed certificate. If you use a self-signed certificate, you must turn off SSL authentication by adding the following to the NETWORK section in the client polite.ini file:

DISABLE_SSL_CHECK=YES

This parameter tells the reverse proxy firewall to use SSL encryption for the communication from the client, but not to perform SSL authentication.