Using Installation Exits

DFSMS provides replaceable modules or exit points for installation exit routines that modify DFSMS system functions. A replaceable module is an IBM-supplied module that you can modify or replace.

Following are the types of replaceable modules or exit locations that are defined as installation exits:

Dummy modules. The IBM-supplied module does not perform a useful function, it just supplies a return code to its caller. For example, the DADSM exit routines are dummy modules.
Functional modules. The IBM-supplied module already performs a useful function. Although you can replace these modules, carefully consider whether you should preserve the IBM-supplied functions. For example, the data management abend installation exit (IFG0199I) is a functional module.
No module. IBM does not supply a module, but does supply an exit point so that you can create an exit routine if you desire. If you do not supply a routine, the exit is not taken. For example, the nonstandard tape label processing exit points do not come with a replaceable module.

Any modules you create for installation exits must be reentrant and refreshable. You can install them during system installation by using SMP/E or you can link-edit the module into the appropriate library.

Installation exits are available at a variety of points in DFSMS processing. The sections for each exit documented in this information specify where in the system's processes the exits are called.