NetBackup deassigns volumes as part of normal operations.

See About assigning and deassigning volumes.

To deassign a volume, you expire the images on the volume. After you expire a volume, NetBackup deassigns it and does not track the backups that are on it. NetBackup can reuse the volume, you can delete it, or you can change its volume pool.

See Expiring backup images.

You can expire backup images regardless of the volume state (Frozen, Suspended, and so on).

NetBackup does not erase images on expired volumes. You can still use the data on the volume by importing the images into NetBackup (if the volume has not been overwritten).

See Importing backups.