Web server tuning parameters

WebSphere Application Server - Express provides plug-ins for several Web server brands and versions. If you are running your Web server on a non-iSeries platform, see the product documentation for performance tuning information. For additional information, refer to Chapter 6 of the Performance Capabilities Reference Manual. This manual is available in the Performance Management Resource Library.

The IBM HTTP Server (powered by Apache) is a multi-process, multi-threaded server. For IBM HTTP Server for i5/OS, you can adjust these settings:

• Access logs
  • Description: The access logs record all incoming HTTP requests. Logging can degrade performance. On iSeries, overhead is minimized, because logging occurs in a separate process from the Web server function.
  • How to view or set:
    1. Open the IBM HTTP Server httpd.conf file, located in the /QIBM/ProdData/HTTPA/conf directory.
    2. Search for lines with the text CustomLog.
    3. To enable a custom access log, remove the hash mark (#) at the beginning of the line.
    4. Save and close the httpd.conf file.
    5. Stop and restart the IBM HTTP Server.
  • Default value: By default, the access log is disabled.
  • Recommended value: Do not enable the access logs.
• ThreadsPerChild
  • Description: This directive specifies the maximum number of concurrent client requests that the server processes at any time. The Web server uses one thread for each request that it processes. This value does not represent the number of active clients.
  • How to view or set: Edit or view the ThreadsPerChild directive in the IBM HTTP Server httpd.conf file.
  • Default value: 40
  • Recommended value: It is recommended that you use the default value, and only increase this value if necessary.
• ListenBackLog
  • Description: This parameter sets the length of a pending connections queue. When several clients request connections to the IBM HTTP Server, and all threads are in use, a queue exists to hold additional client requests. However, if you use the default Fast Response Cache Accelerator (FRCA) feature, the ListenBackLog directive is not used, because FRCA uses its own internal queue.
  • How to view or set: For non-FRCA: Edit or view the ListenBackLog directive in the IBM HTTP Server httpd.conf file.
  • Default value: For IBM HTTP Server 1.3.26: 1024 with FRCA enabled, 511 with FRCA disabled
  • Recommended value: Use the default value.