Not all read-only variable values are significant during the actual operation of any ACS routine. For example, the value of &USER could be null in the storage group selection routine if no user ID had been specified on the JOB statement or determined from the environment.

The user ID (and group ID) is only available if specified using JCL or if RACF® (or any other security product) is active. For example, on a RESTORE, if a user ID is specified, the ACERO passed by DFSMSdss does not contain the user ID, and because RACF is not active, DFSMS does not interrogate the ACEE to fill it in.