As discussed in section “Saving BS2000 files and job variables”, not only catalog entries (save type MIGF) but also the data of migrated files can be saved during backups.
If the data from migrated files is to be included in the backup, it is not advisable to place the backup of files migrated to S1 on the S1 pubset. If this pubset were to fail, it would affect the data and the backup of that data. However, the BACKUP-FILES statement supports the TO-STORAGE operand, which provides a mechanism with which to perform a backup to any pubset in this particular situation.
During the restore, the HSMS administrator can specify whether just the catalog entries or the catalog entries and the data of the migrated files should be copied to storage level S0. It is also possible to restore the data of the migrated files to a migration level.