A brief introduction to z/OS system configuration

In the simplest case, z/OS® is configured by changing partitioned data set (PDS) members in the data sets SYS1.PROCLIB, SYS1.PARMLIB, and a few other important data sets including site-specific partitioned data sets.

Most configuration (parmlib) member names consist of a predefined name with a two character suffix added. A common convention is to refer to the suffix as xx, so you often see references to LOADxx, IEASYSxx, and so on. Configuration files refer to other members by a keyword and suffix number. For example, a member that is called IEASYSRC might identify the main z/OS UNIX configuration file with the line OMVS=RC, which means that z/OS UNIX finds the member that contains its configuration parameters by starting with a predetermined name, BPXPRM, and add the suffix RC (resulting in member name of BPXPRMRC). The keywords in the configuration files are not usually the same as the member name prefixes.

Important: Do not directly update data sets such as SYS1.PARMLIB and SYS1.PROCLIB. Some installation-specific libraries are searched before the SYS1 data sets, leaving the SYS1 libraries with IBM® supplied defaults.

This z/OS 2.3 ADCD defines several sets of alternative libraries. The configurations for the distribution itself are stored in a set of libraries that start with the qualifiers ADCD.*. The set of libraries that are used to store ZD&T configurations start with the qualifiers FEU.*. This z/OS distribution also provides a set of libraries for you to use, which start with the high-level qualifier USER. This z/OS distribution is already set up to read from most of the USER libraries before the FEU.* libraries and the ADCD.* libraries. The USER.* libraries are initially empty, and you can use them for your own changes. They are on a separate volume, A3CFG1. Avoid updating the ADCD.* and SYS1.* libraries whenever possible. If you choose to place data in the USER data sets, or create other user data sets or customizations in xxCFG1, these data sets can be easily migrated to a new system. Since volume names change with each release of a z/OS ADCD for ZD&T, add the xxCFG1 volume to the devmap for the new system, and then copy any customized files back to the newer xxCFG1 volume.

The customizations described here use USER.* libraries, which tend to be commonly available in any z/OS distribution. While you follow these instructions, all changes are made in USER.* libraries, except for adding LOADPARM members to SYS1.IPLPARM.

Note: Subsystem configuration changes, such as CICS® definitions, also change original libraries such as the CICS CSD.