Preemption of Client or Server Operations
The server can preempt server or client operations for a higher priority operation when a mount point is in use and no others are available, or access to a specific volume is required.

Mount Point Preemption
The following are high priority operations that can preempt operations for a mount point:
v Backup database
v Restore
v Retrieve
v HSM recall
v Export
v Import
The following lists operations that can be preempted and are listed in order of
priority. The server selects the lowest priority operation to preempt, for example reclamation.
1. Move data
2. Migration from disk to sequential media
3. Backup, archive, or HSM migration
4. Migration from sequential media to sequential media
5. Reclamation
You can disable preemption by specifying NOPREEMPT in the server options file.
When this option is specified, the BACKUP DB command is the only operation
that can preempt other operations.

Volume Access Preemption
A high priority operation that requires access to a specific volume currently in use by a low priority operation can automatically preempt the operation. For example, if a restore request requires access to a volume in use by a reclamation process and a drive is available, the reclamation process is canceled and message ANR0494I or ANR1441I is issued.
The following are high priority operations that can preempt operations for access to a specific volume:
v Restore
v Retrieve
v HSM recall

The following lists operations that can be preempted, and are listed in order of
priority. The server preempts the lowest priority operation, for example reclamation.
1. Move data
2. Migration from disk to sequential media
3. Backup, archive, or HSM migration
4. Migration from sequential media
5. Reclamation
You can disable preemption by specifying NOPREEMPT in the server options file.
When this option is specified, no operation can preempt another operation for
access to a volume.