About selecting media in robots

When NetBackup receives a request for a volume, it searches the EMM database for the media ID. The external media ID should correspond to the NetBackup media ID.

A request for a volume includes the following attributes:

The media ID
The device density
The file name that is used to link to the device that is assigned.

Table: How NetBackup selects a volume in a robot describes the order in which NetBackup selects a volume in a robot.

Table: How NetBackup selects a volume in a robot

Order	Description
1.	NetBackup searches the media catalog for a volume that is already mounted in a drive and meets the following criteria: Configured to contain backups at the retention level that the backup schedule requires. However, if the NetBackup Media host property Allow multiple retentions per media is specified for the server, NetBackup does not search by retention level. In the volume pool that the backup job requires. Not in a FULL, FROZEN, IMPORTED, or SUSPENDED state. Of the same density that the backup job requested, and in the robot that the backup job requested. Not currently in use by another backup or a restore. Not written in a protected format. NetBackup detects the tape format after the volume is mounted. If the volume is in a protected format, NetBackup unmounts the volume and resumes the search. If a suitable volume is found, NetBackup uses it.
2.	If NetBackup cannot find a mounted volume that satisfies all of the previous conditions, it checks the media catalog for any volume that is suitable. If a suitable volume is in a robot, NetBackup issues the commands that move the volume to a drive, position the heads to the beginning of the volume, and assign it to the request. No manual intervention is required. If a suitable volume is not in a robot but is in a standalone drive, NetBackup automatically mounts and assigns it. No manual intervention is required. If a suitable volume is not in a robot or a standalone drive and the request is media-specific, NetBackup may pend a mount request. A media-specific mount request is one for a restore, for an import, or from the tpreq command. If a suitable volume is not in a robot or a standalone drive, NetBackup may attempt to use another volume only as follows: For backup jobs for which any other media can be used.
3.	If a suitable volume does not exist or if a suitable volume is at end of media (EOM), NetBackup assigns a new volume. NetBackup may assign a new volume even if a volume is not full (because NetBackup received an EOM message from the drive). The new volume must meet all of the following criteria: Is the correct media type Is for the correct robot type (if applicable) Is located in the requested robotic peripheral (if applicable) Resides on the requested host Is in the correct volume pool Is not currently assigned (not already allocated to NetBackup) Is not expired (if an expiration date is defined in NetBackup) Has not exceeded the maximum number of mounts allowed
4.	If more than one volume qualifies, NetBackup chooses the volume that was least recently used. NetBackup then adds it to the media catalog and assigns it the specified retention level.
5.	If there are no unassigned volumes of the requested type, the backup terminates with an error message that no media were available. NetBackuptakes no action.

See About spanning media with automatic media selection.

About selecting media in robots

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