Web server plug-in tuning tips

Important tips for web server plug-in tuning include how to balance workload and improve performance in a high stress environment. Balancing workloads among application servers in a network fronted by a web server plug-in helps improve request response time.

[z/OS]This product uses the z/OS® native Workload Management (WLM) functionality to dynamically balance the workload of application servers defined to a z/OS HTTP Server, Version 5.3, or an IBM® HTTP Server for WebSphere® Application Server on z/OS See the z/OS publication HTTP Server Planning, Installing and Using for more information about the z/OS HTTP Server, Version 5.3. Information about the IBM HTTP Server for WebSphere Application Server on z/OS is contained in this documentation.

Limiting the number of connections that can be established with an application server works best for web servers that follow use a single, multithreaded process for serving requests.

[z/OS]IBM HTTP Server typically uses multiple multithreaded processes for serving requests. Specify the following values for the properties in the web server configuration file (httpd.conf) to prevent the IBM HTTP Server from using more than one process for serving requests.

ServerLimit           1
ThreadLimit           1024
StartServers          1
MaxClients            1024
MinSpareThreads       1
MaxSpareThreads       1024
ThreadsPerChild       1024
MaxRequestsPerChild   0

Improving performance in a high stress environment

To tune the TcpTimedWaitDelay setting, change the value of the tcp_time_wait_interval parameter from the default value of 240 seconds, to 30 seconds:
  1. Locate in the Windows Registry: 
    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\tcpip\Parameters\TcpTimedWaitDelay
    If this entry does not exist in your Windows Registry, create it by editing this entry as a new DWORD item.
  2. Specify, in seconds, a value between 30 and 300 inclusive for this entry. (It is recommended that you specify a value of 30. )
To tune the MaxUserPort setting:
  1. Locate in the Windows Registry: 
    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\tcpip\Parameters\MaxUserPort
    If this entry does not exist in your Windows Registry, create it by editing this entry as a new DWORD item.
  2. Set the maximum number of ports to a value between 5000 and 65534 ports, inclusive. (It is recommended that you specify a value of 65534,)

See the Microsoft website for more information about these settings.