Application server tuning parameters

You can tune application server settings to control how an application server provides services for running applications and their components. Each application server instance contains interrelated components, called a queuing network, that must be properly tuned to support the specific needs of your e-business application. The queuing network helps the system achieve maximum throughput and maintain the overall stability of the system. For more information about the queuing network, see Queuing network.

You can tune the following application server settings:

• Web container
• Session management
• Data sources
• Process Priority

Web container

Each application server includes a Web container. The application server routes servlet requests along a transport queue between the Web server plug-in and the Web container. Default Web container properties are set for simple Web applications. However, these values might not be appropriate for more complex Web applications. You can adjust these parameters to tune the Web container based on the specific needs of your environment:

• Thread pool Maximum size
  • Description: This value limits the number of requests that your application server can process concurrently. For more information, see Thread pool settings.

    Note: The information on the settings page applies to all thread pools in WebSphere Application Server - Express.

  • How to view or set:
    1. Start the administrative console.
    2. In the topology tree, expand Servers and click Application Servers.
    3. Click the name of the application server that you want to configure.
    4. Click Web Container.
    5. On the Web Container page, click Thread Pool.
    6. Specify a value for the Maximum size field.
    7. Click Apply or OK.
    8. Save the configuration.
    9. Stop and restart the application server.
  • Default value: 50
  • Recommended value: This value should be set to handle the peak load on your application server. It is recommended that you specify a maximum size less than or equal to the number of threads processing requests in your HTTP server. A value in the range 25-50 is generally a good starting point.
• Growable thread pool
  • Description: This setting specifies whether the number of threads can increase beyond the maximum size configured for the thread pool. For more information, see Thread pool settings.
  • How to view or set:
    1. Start the administrative console.
    2. In the topology tree, expand Servers and click Application Servers.
    3. Click the name of the application server that you want to configure.
    4. Click Web Container.
    5. On the Web Container page, click Thread Pool.
    6. Select Allow thread allocation beyond maximum thread size.
    7. Click Apply or OK.
    8. Save the configuration.
    9. Stop and restart the application server.
  • Default value: Disabled
  • Recommended value: It is recommended that you do not enable this property if you are confident the thread pool maximum size is large enough to adequately process the peak load on your application server. If you want to allow the thread pool to exceed the configured maximum pool size, enable this property. This setting is beneficial if the application server receives an unexpected increase in requests or if the maximum pool size is set too low. In this scenario, additional threads are created to handle the increased number of requests. These connections are destroyed when the number of requests returns to its typical level. However, enabling the growable thread pool setting might cause a large number of threads to be created, and can have a negative impact on system storage and performance.

You can also tune several custom parameters for HTTP transports in the Web container. For more information, see Set custom properties for an HTTP transport.

Session management

The installed default settings for session management are configured for optimal performance. For more information, see Tune session management in Application development and Tuning parameter settings.

Data sources

Applications uses data sources to access databases. The following data source settings can affect performance:

• Connection pooling For moreinformation about connection pooling, see Connection pooling in Application Development and Connection pool settings.
  • Maximum connection pool
    • Description: This value specifies the maximum number of managed connections for a pool.
    • How to view or set:
      1. Start the administrative console.
      2. In the topology tree, expand Resources and click JDBC Providers.
      3. Click the name of the provider for the data source that you want to configure.
      4. Click Data Sources.
      5. Click the name of the data source that you want to configure.
      6. Click Connection Pool.
      7. Specify a value in the Max Connections field.
      8. Click Apply or OK.
      9. Save the configuration.
      10. Stop and restart the application server.
    • Default value: 10
    • Recommended value: Set the value for the connection pool lower than the value for the Max Connections option in the Web container. If the pool is larger than necessary, it might waste memory and other system resources. A setting of 10-25 is suitable for many applications. For additional about connection pool size, see Queuing network.
  • Minimum connection pool
    • Description: This value specifies the minimum number of managed connections for a pool.
    • How to view or set:
      1. Start the administrative console.
      2. In the topology tree, expand Resources and click JDBC Providers.
      3. Click the name of the provider for the data source that you want to configure.
      4. Click Data Sources.
      5. Click the name of the data source that you want to configure.
      6. Click Connection Pool.
      7. Specify a value in the Min Connections field.
      8. Click Apply or OK.
      9. Save the configuration.
      10. Stop and restart the application server.
    • Default value: 1
    • Recommended value: Set the minimum pool size to handle the average load on the system.
• Statement cache size
  • Description: WebSphere Application Server - Express provides a statement cache for each data source. This value represents the number of free prepared statements per connection in the connection pool. The statement cache stores query information for the data source. You can adjust to size of the statement cache to optimize performance. For more information, see Data source settings.
  • How to view or set:
    1. Start the administrative console.
    2. In the topology tree, expand Resources and click JDBC Providers.
    3. Click the name of the provider for the data source that you want to configure.
    4. Click Data Sources.
    5. Click the name of the data source that you want to configure.
    6. Specify a value in the Statement Cache Size field.
    7. Click Apply or OK.
    8. Save the configuration.
    9. Stop and restart the application server.
  • Default value: 10
  • Recommended value: In most situations, it is recommended that you set this to the number of unique statements for each application that uses the datasource. Setting the cache size to this value avoids cache discards, and generally results in the best performance. However, if the cache is too large, it might cause performance problems as a result of increased cache management and increased use of system resources. If you have a large number of unique statements, a smaller number might be appropriate. For information about tuning the statement cache size, see Tuning the WebSphere Prepared Statement Cache.

Process Priority

• Description: The priority setting establishes the application server job's run priority. The default process priority is 25. The application server does not override the default behavior of Java thread creation. Worker threads within the server are configured to run at 6 levels lower than the job's run priority. Therefore, by default, the priority of the worker threads is 31. For more information about this setting, see Process execution settings.
• How to view or set:
  1. Start the administrative console.
  2. In the topology tree, expand Servers and click Application servers.
  3. Click the name of the application server that you want to configure.
  4. Click Process Definition.
  5. Click Process Execution.
  6. On the Process Execution page, specify a value in the Process Priority field.
  7. Click Apply or OK.
  8. Save the configuration.
  9. Stop and restart the application server.
• Default value: 25
• Recommended value: In most situations, the default value is acceptable. However, if other workloads are running at a higher priority (that is, with a lower priority number), you might need to adjust the application server's priority so that it can more easily access the necessary resources.