CA IDMS Tuesday Tip by Edward Gorga, Principal Support Engineer for July 23, 2013.
The startup parameter STEPLIB=Y (or STEP=Y) forces IDMS to load modules RHDCCKUR and RHDCTCKR from the STEPLIB instead of the CDMSLIB.
There are two situations where you need to specify STEPLIB=Y:
[list]
[*]z/OS is running with AllowUserKeyCSA(NO)
[*]#SVCOPTS specifies AUTHREQ=YES
[list]
In these situations IDMS needs to run in an alternate protect key and these modules need to be loaded from an APF authorized STEPLIB.