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6.6.31: Monitoring and tuning performance (overview) >
6.6.31.1: Monitoring and tuning performance with the Java administrative console >
6.6.31.1.1: Using the Performance Tuner Wizard of the Java administrative console

6.6.31.1.1: Using the Performance Tuner Wizard of the Java administrative console

Open the Performance Tuner Wizard by clicking Console-> Wizards-> Performance Tuner from the WebSphere Advanced Edition administrative console.

Using the Performance Tuner Wizard

Use this wizard to tune the most common performance related settings associated with one of your application servers or one of your server groups. Optimize performance by working with settings for your applications, servlets, enterprise beans, data sources, and expected load.

Application Server

Select the application server or server group to tune.

If you are tuning a server group, all updates will be reflected in the server group and only some will be propagated to existing clones (see the server group property reference for details). Subsequently created clones will be based on the updated server group values.

Web Container

Update the pool size within the normal range by adjusting the slider. Edit the numeric field to update the pool size within, or outside the normal range. Think about specifying the maximum number of Web container threads less than the number of connections accepted by the Web server. Consider setting the Web container maximum threads number significantly smaller than the number of connections accepted by the Web server, for a site with many static pages returned directly by the Web server.

ORB Properties

You can tune the following object request broker properties:

  • Pass by Reference

    This option can provide better performance. Select Pass by Reference, only if appropriate for your application. Selecting this option can break remote transparency, since you can modify objects passed to an EJB method. Know your application before using this option.

  • ORB Threads Pool Size

    A thread is needed for each EJB request. Enterprise beans are typically invoked from servlets in another JVM, using RMI/IIOP and remote EJB client applications, using RMI/IIOP. The ORB thread pool size should accommodate both request sources.

Data Source

Select a data source that is associated with the selected application server. After selecting the data source, click Next. You are given the opportunity to tune the corresponding:

  • Connection pool size
  • Prepared statement cache size
  • Database (for DB2 only)

Data Source: Connection Pool Size

Each data source contains a pool of connections to the corresponding database. An upper bound for your application comes from the sum of the number of Web container threads and ORB threads.

The servlet contribution to the connection pool size can be significantly smaller than the Web container maximum threads, if only a small percentage of servlet requests use these database connections.

Data Source: Prepared Statement Cache Size

Make your prepared statement cache large enough for all prepared statements, by setting the cache size to the product of:

  • The number of SQL prepared statements in your application
  • The maximum number of configured data source connections

Database: (DB2 Only)

This panel is only available for DB2 databases.

Tune the database after this wizard has completed, by selecting Tune database and entering the DB2 SYSADM ID and password. If you provided a cataloged database alias name when configuring the data source and this alias name differs from the real database name, enter the real database name in the field provided.

After database tuning is selected, and you have completed the remaining panels, click Finish on the Summary panel. The tuning wizard then calls the DB2SmartGuide API, to tune the DB2 database associated with the data source. Stop and restart the database instance, for the DB2SmartGuide changes to take effect.

Note: DB2SmartGuide tuning works better if the database is already populated. It is not necessary or recommended to tune the repository database (WAS).

Before tuning a database, you might want to use the DB2 DBA utility to back up (db2cfexp) the database configuration. If the tuning fails, you can then restore (db2cfimp) your database configuration. You can also use:

  • DB2 RESET DATABASE CONFIGURATION FOR database-name
    to restore the database to default values
  • DB2 RESET DATABASE MANAGER CONFIGURATION
    to restore the DBM to default values

The database being tuned must reside on a DB2 Server at Version 7.2.1, or higher. This tuning option is not available in DB2 servers for OS/390, OS/400, VM or VSE.

Java Virtual Machine (JVM) Heap Size

The Java Virtual Machine (JVM) Heap Size settings influence garbage collection of Java objects. If you increase the heap size, garbage collection occurs less frequently, but takes longer.

These settings depend strongly on your application and on the amount of physical memory available. Consider:

  • whether the JVM Heap for the selected application server shares physical memory with other application server JVM Heaps on the same machine.
  • specifying JVM Heaps to reside in physical memory and prevent swapping to disk.
  • setting the starting JVM Heap Size to one quarter of the maximum JVM Heap Size.
  • setting the maximum JVM Heap Size to the following, if you have only one application server on the machine:
    • 128 MB, for small systems with less than 1 GB of memory
    • 256 MB, for systems with 2 GB of memory
    • 512 MB, for larger systems

Note: A value of 0, or blank, indicates that no starting or maximum heap size is passed, when initializing the JVM.

On OS/400, the JVM Heap Size is quite different and you should never set the maximum heap size.

Summary:

The following performance settings are saved in the WebSphere Application Server configuration when you click Finish. Correct a setting without updating the configuration, by clicking Back.

After you click Finish, warnings are displayed for any of the following conditions:

  • Any of the following parameters are changed to a value greater than the highest value on the corresponding slider:
    • Web Container Maximum Threads
    • ORB Thread Pool Size
    • Data Source Maximum Connections
    • Data Source Prepared Statement Cache Size
    • JVM Maximum Heap Size
  • A database is ready for tuning. The warning notifies you about restarting the DB2 database instance and suggests that you back up your database configuration before tuning.
  • The number of Web Container Threads and ORB Threads is greater than a Data Source Connection Pool.

If these conditions are acceptable to you, then continue. If these conditions are not acceptable, return to the wizard to change a setting, or cancel the tuning session.

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