The fast subsequent migration function allows unchanged data sets that are recalled from ML2 tape to be reconnected to the same ML2 tape. Data sets must meet standard migration eligibility checks as well as a reconnectability check to be eligible for reconnection. The fast subsequent migration function occurs for non-VSAM data sets and for VSAM data sets that have no defined alternate indexes or paths.

Once a data set that is recalled from tape meets normal eligibility criteria, the fast subsequent migration (a fast remigrate) occurs during volume migration. Fast subsequent migrations occur ahead of migrations that cause data movement. Because the data is still on tape from the previous migrate, the fast subsequent migration involves both creating and updating DFSMShsm control records. It does not involve moving the data to tape.

Reconnection can occur during individual data set migration or during volume migration. See z/OS DFSMShsm Storage Administration for more information on fast subsequent migration.