USERMOD SYSMOD: Customizing an element

If you had a requirement for a product to perform differently from the way it was designed, you might want to customize that element of your system. IBM® provides you with certain modules that allow you to tailor IBM code to meet your specific needs. After making the desired changes, you add these modules to your system by installing a USERMOD SYSMOD.

This SYSMOD can be used to replace or update an element, or to introduce a totally new user-written element into the system. In either case, the USERMOD SYSMOD is built by you either to change IBM code or to add your own code to the system.

In Figure 1, MOD3 has been updated through the installation of a USERMOD SYSMOD.

Figure 1. Customizing an element

Figure 2 shows an example of a simple USERMOD SYSMOD.

Figure 2. Example of a simple USERMOD SYSMOD

++USERMOD(USRMOD1)             /* SYSMOD type and identifier.   */.
++VER(Z038) FMID(FUN0001)      /* Apply to this product         */
            PRE(UZ00004)       /* at this service level.        */.
++SRCUPD(JESMOD3)              /* Update this source module     */
            DISTLIB(AOSFB)     /* in this distribution library. */.
...
... update control statements
...

PTF, APAR, and USERMOD SYSMODs all have the function SYSMOD as a prerequisite. In addition to their dependencies on the function SYSMOD:

PTF SYSMODs might be dependent upon other PTF SYSMODs.
APAR SYSMODs might be dependent upon PTF SYSMODs and other APAR SYSMODs.
USERMOD SYSMODs might be dependent upon PTF SYSMODs, APAR SYSMODs, and other USERMOD SYSMODs.

Sometimes a PTF or even an APAR is dependent upon other PTF SYSMODs called corequisites. Consider the complexity of these dependencies– When you multiply that complexity by hundreds of load modules in dozens of libraries, the need for a tool like SMP/E becomes apparent.