The system creates a preallocated multivolume data set for system-managed
DASD if the storage class has GUARANTEED_SPACE=YES and one of the
following:
- The data class has a volume count greater than one
- You specify two or more volume serial numbers
- You specify a volume count greater than one on the VOLUME parameter.
If you choose specific volume serial numbers, the system uses these
volumes; otherwise, the system selects the volumes.
Note: All tape volumes in a multivolume data set must reside
in the same system-managed tape library and in the same storage group.