Explanation: DISASTERMODE is an optional parameter that specifies whether DFSMShsm establishes a tape substitution mode. This command plays an important part during an actual disaster recovery or when you are running a disaster recovery test.
While DFSMShsm is running in disaster mode, recalls and recovers from tape volumes that are flagged as having disaster alternate volumes dynamically substitute the alternate tape for the original tape. For more information on the use of disaster alternate volumes, refer to Making disaster backup copies of DFSMShsm-owned tape volumes.
If you specify Y for this parameter on the SETSYS command, DFSMShsm checks the TTOC record of the original tape volume to see if a disaster alternate volume exists and if so, requests the use of it to return the data. If you specify N for this parameter on the SETSYS command or no disaster alternate volume exists, DFSMShsm will request the original tape volume and makes no substitution.
SMS relationship: Parameter has the same meaning when applied to SMS-managed or non-SMS-managed DASD volumes or data sets.
SETSYS default: If you specify DISASTERMODE without specifying any subparameter, the default is Y.
DFSMShsm default: If you do not specify this parameter on any SETSYS command, the DFSMShsm default is N.