You should understand how Snapshot copies are used during an SMTape baseline backup and an incremental backup. There are also considerations to keep in mind while performing a backup using SMTape.
While performing a baseline backup, you can specify the name of the Snapshot copy to be backed up to tape. If no Snapshot copy is specified, then depending on the access type of the volume (read/write or read-only), either a Snapshot copy is created automatically or existing Snapshot copies are used. When you specify a Snapshot copy for the backup, all the Snapshot copies older than the specified Snapshot copy are also backed up to tape.
If you do not specify a Snapshot copy for the backup, the following occurs:
The newly created Snapshot copy and all the older Snapshot copies are backed up to tape.
Any new Snapshot copies created after the backup is started are not backed up.
For SMTape incremental or differential backup operations, the NDMP-compliant backup applications create and manage the Snapshot copies.
You must always specify a Snapshot copy while performing an incremental backup operation. For a successful incremental backup operation, the Snapshot copy backed up during the previous backup operation (baseline or incremental) must be on the volume from which the backup is performed. To ensure that you use this backed-up Snapshot copy, you must consider the Snapshot policy assigned on this volume while configuring the backup policy.
You should not use these Snapshot copies for SMTape backup.
During the backup operation, SMTape locks the Snapshot copy on the destination volume and if the corresponding Snapshot copy is deleted on the source volume, then the subsequent SnapMirror update operation fails.
You should not use these Snapshot copies during incremental backup.