When DFSMShsm selects a backup volume, it considers whether this is initial volume selection or subsequent volume selection.
If an error occurs during the selection process for a tape and the error is associated with a particular volume, DFSMShsm considers the tape backup volume unavailable for backup processing and selects another backup volume. Each time DFSMShsm is started, all nonfull backup volumes are considered available for backup processing.
The error handling and tape selection process differs when using the duplex tape option for your backup tapes.
When the backup function is not using a system-managed tape library, UNITTYPE specifies that only tape backup volumes capable of being mounted and written to on the specified type of unit are selected for output during backup processing.
DFSMShsm backs up users’ data sets to daily backup volumes during volume backup. Daily backup volumes either are assigned by the storage administrator to a day in the backup cycle before DFSMShsm uses them or are assigned when DFSMShsm selects a volume added as a backup volume.
DFSMShsm stops the search as soon as it finds an acceptable volume. If it does not find an acceptable volume, DFSMShsm stops processing the requested backup function.
If an error occurs during the selection process and the error is associated with a particular volume, DFSMShsm considers the volume unavailable for backup processing and selects another daily backup volume. Each time DFSMShsm is started, the target volumes previously considered unavailable for backup processing are reinstated as available volumes.
After a volume backup task has obtained a daily backup volume, it continues to use that volume until the volume is no longer needed, the volume becomes full, or certain error conditions occur.
Now consider the processing that occurs when you specify the backup device categories of DASD, TAPE, or NONE.