When volume reference (VOL=REF) is used, the storage group of the referenced data set is passed to the ACS routines in the &STORGRP read-write variable. However, keep in mind the following:

• The storage group name might not be available if the reference is to a data set on SMS-managed tape. This is because private tapes can be entered into a tape library with a blank storage group name. In this case, the AS routine should use the &LIBNAME read-only variable to determine the storage group for the referenced data set. In this case, the referenced and referencing data sets must reside in the same storage group.
• If the reference is to a new data set, there can be multiple candidate storage groups for the referenced data set and the actual storage group might not have been selected yet. In this case, only the first candidate storage group is passed as input to the ACS routines, and this might not be the storage group in which the referenced data set is eventually allocated.