IBM HTTP Server V5.3 for z/OS: Part 1: Planning

Various capabilities in IBM® HTTP Server V5.3 for z/OS® are available in IBM HTTP Server, but implemented differently. Learn about key differences in installation and migration that are important for planning.

The part and chapters correspond to the part and chapters in publication number SC34-4826-09 of the z/OS HTTP Server Planning, Install, and Using guide for IBM HTTP Server V5.3 for z/OS.

The following topics are applicable to chapter 1:

The following topic is applicable to chapter 2:

Configuration and administration

You can administer IBM HTTP Server only by updating the EBCDIC configuration files.

z/OS UNIX System Services

z/OS UNIX System Services user ID and UID
IBM HTTP Server runs in a UNIX process under a user ID of your choice, such as WWWSERV. Ensure that the z/OS UNIX System Services UID is not 0 . Read the Performing required z/OS system configurations topic for information about the user ID and UID.
BPX.SERVER facility
If you change the thread identity of logged in users by using the SAFRunAs directive, permit the web server ID READ acess in the BPX.SERVER facility.

DLL considerations

Add the DLL path to the LIBPATH statement in the install_root/bin/envvars file.

Fast Response Cache Accelerator

The Fast Response Cache Accelerator is not supported on the z/OS operating system for IBM HTTP Server. As alternatives, use the mod_cache, mod_cache_disk, and mod_file_cache modules for caching.

Best practice: Cache remote or dynamic files instead of static files. An exception is the caching of static files with the mod_file_cache module. This module speeds up static file access.

For more information about the modules, read the Apache HTTP Server documentation.

MVSDS DLL z/OS data set considerations

IBM HTTP Server does not cache or preload MVS™ data sets.


Tune your server by using the performance and tuning information for the IBM HTTP Server.

Maximum active threads

IBM HTTP Server V5.3 for z/OS uses the MaxActiveThreads directive to set the maximum number of threads that can be active at one time. IBM HTTP Server uses a hybrid model with multiple thread processes. This hybrid model uses multiple directives to manage the processes.

The MAXClients directive determines the limit for the total number of process threads. The ThreadLimit and ThreadsPerChild directives affect how many threads are created for each process. The ServerLimit, MaxClients, and ThreadsperChild directives control the maximum number of processes created.
Best practice: Use the configuration in the httpd.conf default configuration file until your server needs to process more concurrent requests. When you change the MaxClients directive and ServerLimit directives, increase or decrease their values by the same factor.

For more information about the directives, read the Apache HTTP Server documentation.

How to code directives to improve web server performance

The following directives are disabled in the default httpd.conf configuration file for IBM HTTP Server. Use caution when you enable these directives as they can have an affect on your web server performance.

       Options FollowSymlinks

For more information about these directives, read the Apache HTTP Server documentation.

Workload management

Follow the directions in the topic on classifying HTTP requests for workload management (WLM) to implement WLM for IBM HTTP Server.

Migration considerations for installation

Whether you are initially installing IBM HTTP Server or are migrating to a later version after your initial installation, follow the instructions for the Installing fix packs on IBM HTTP Server using the Installation Manager GUI topic.