If DFSMShsm migrates a data set, subsequent access to the data set while it is migrated must cause allocation to do a catalog LOCATE or OPEN must be issued to cause the data set to be automatically recalled. For example, if the volser and unit are specified on a SYSPROC DD statement in a TSO logon procedure, a problem exists if that data set is migrated. The problem exists because no catalog LOCATE is done by allocation and no OPEN is performed in TSO unless the volume specified is an SMS-managed volume.

DFSMShsm does not migrate data sets having SYS1 as the first qualifier unless a SETMIG LEVEL request has been issued to remove this restriction. For other data sets used in the above manner, the system programmer must either not specify the volser and unit (which causes a catalog LOCATE by allocation), or specify the names of the data sets on SETMIG commands placed in the DFSMShsm startup member to prevent them from migrating.