When a data set stacking inconsistency is detected, the ACS routines are re-invoked. When they are available, the following values are passed as input to the ACS routines:

• The storage group of the primary data set
• The storage class of the primary data set
• The management class selected by the previous invocation of the management class ACS routine for the stacked data set
• The data class selected by the previous invocation of the data class ACS routine for the stacked data set

Values might not be available for the following reasons:

• No storage class and storage group is available from the primary data set if it is directed to non-SMS-managed media.
• No management class is available for the stacked data set if it was initially assigned no storage class.
• If SMS was invoked by JES3, it is unable to access the work areas to obtain the storage class, management class, or data class.
• The storage group name might not be available if the primary data set is 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 ACS routine should use the &LIBNAME read-only variable to determine the storage group for the stacked data set. In this case, the primary data set and the stacked data set must reside in the same storage group.
• If the primary data set is new, there might be multiple candidate storage groups for it 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 primary data set is eventually allocated.