A frozen volume is unavailable for future backups. A frozen volume never expires, even after the retention period ends for all backups on the media. The media ID is never deleted from the NetBackup media catalog, and it remains assigned to NetBackup. A frozen volume is available for restores. If the backups have expired, you must import the backups first.

NetBackup freezes media automatically when read or write errors surpass the threshold within the time window. The default media error threshold is 2. That is, NetBackup freezes media on the third media error in the default time window (12 hours).

NetBackup also freezes a volume if a write failure makes future attempts at positioning the tape unreliable.

Common reasons for write failures are dirty write heads or old media.The reason for the action is logged in the NetBackup error catalog (view the Media Logs report or the All Log Entries report).

You can use the NetBackup nbemmcmd command with the -media_error_threshold and -time_window options to change the default values.

Additional information about nbemmcmd is available.

See the NetBackup Commands guide.

To reverse a freeze action, use the bpmedia command to unfreeze the volume.