DFSMS contains three sample ACS installation exits: one each for data class, storage class, and management class. After each ACS routine runs, the corresponding ACS exit routine is called. In an exit, you can call other programs or services. The parameters passed to the exit are the same as the ACS routine read-only variables.

You can also use installation exits to override the ACS-assigned classes or to alter the ACS variables and rerun the ACS routine.

A storage class ACS exit is provided in the SYS1.SAMPLIB distributed in the Custom Built Installation Processing Option (CBIPO) product for the z/OS® operating environment. You can use it to display all the ACS variables for an allocation, or to debug any ACS routine design or coding errors.

If you do not need these installation exits, do not supply dummy exits. Otherwise, you incur unnecessary overhead.

Tip: A pre-ACS routine exit is available with the VTS Export/Import SPE. The purpose of this exit is to let tape management systems provide read-only variables to the ACS routines to facilitate tape-related decision making.

Related Reading: For more information on using installation exits, see z/OS DFSMS Installation Exits.