The data is copied from a backup copy or another VSAM data set, and is imported to the target data set. If a storage class is assigned, the data is then copied into a system-managed target data set. Otherwise it is copied into a non-system-managed target data set. The data class ACS routine is not invoked, because either the data set already exists, or the characteristics of the data set are derived from the IDCAMS IMPORT job.
The storage class ACS routine is invoked to determine whether the data set is system-managed. The imported data might come from a non-system-managed source data set that was then copied into a system-managed target data set.
The management class ACS and storage group ACS routines are invoked only if the data set is system-managed and a storage class was assigned.