What are SYSMODs?

Software, whether it is a product or service, consists of elements such as macros, modules, source, and other types of data (such as CLISTs or sample procedures). For software to be installed by SMP/E, it must include control information for the elements. This information describes the elements and any relationships the software has with other products or service that may also be installed on the same system. The combination of elements and control information is called a system modification, or SYSMOD.

There are four types of SYSMODs:

Function SYSMODs (or functions). These introduce a new product, a new version or release of a product, or updated functions for an existing product into the system.
There are two types of function SYSMODs:
- A base function either adds or replaces an entire functional area in the system. Examples of base functions are SMP/E and MVS™.
- A dependent function provides an addition to an existing functional area in the system. It is called dependent because its installation depends on a base function already being installed. Examples of dependent functions are the language features for SMP/E.
PTFs. These are IBM-supplied, tested fixes for reported problems. They are meant to be installed in all environments. PTFs may be used as preventive service to avoid certain known problems that may have not yet appeared on your system, or they may be used as corrective service to fix problems you have already encountered. The installation of a PTF must always be preceded by that of a function SYSMOD, and often other PTFs as well.
APAR fixes. Authorized program analysis reports (APARs) are temporary fixes designed to fix or bypass a problem for the first reporter of the problem. These fixes may not be applicable to your environment. The installation of an APAR must always be preceded by that of a function SYSMOD, and sometimes of a particular PTF. That is, an APAR is designed to be installed on a particular preventive-service level of an element.
User modifications (USERMODs). These are SYSMODs built by you, either to change IBM® code or to add independent functions to the system. The installation of a USERMOD must always be preceded by that of a function SYSMOD, sometimes certain PTFs, APAR fixes, or other USERMODs.
Note: If you want to package a user application program or new system function in SMP/E format, the correct way is to build a base or dependent function SYSMOD, not a USERMOD.

Figure 1 shows the hierarchy of the various SYSMOD types. This example shows two service chains: one for the base function HZY1101 and one for the dependent function JZY1121.

Figure 1. Example of a SYSMOD hierarchy

Example of a SYSMOD hierarchy that has two service chains

SMP/E keeps track of the functional and service levels of each element and uses the SYSMOD hierarchy to determine such things as which functional and service levels of an element should be installed and the correct order for installing updates for elements. For more information about how SMP/E determines the processing order of changes, as well as the functional and service levels of elements, refer to the sections on the APPLY command and the, ACCEPT command in SMP/E for z/OS Commands.