Explanation: STACK | NOSTACK are optional parameters you can use to specify to the ARECOVER DATASETNAME processing whether or not the ABACKUP output was stacked. When the ABACKUP output files are stacked, the ARECOVER processing will allocate file sequence number four.
STACK specifies that DFSMShsm stacked the ABACKUP output files onto a minimum number of tape volumes during ABACKUP processing.
NOSTACK specifies that DFSMShsm did not stack the ABACKUP output files during ABACKUP processing. The NOSTACK parameter allows an installation the capability to ARECOVER backups performed on a down-level version of DFSMShsm.