通过NBU备份间歇性的备份失败，通过日志发现为000173磁带写入的时候就会失败，查看了磁带的使用情况，000173号磁带size为0，不知道是什么原因？
NBU备份错误日志：
11/09/2022 04:01:03 - Info bptm (pid=23291) Waiting for mount of media id 000173 (copy 1) on server WZ_SERVER.
11/09/2022 04:01:03 - mounting 000173
11/09/2022 04:01:06 - Error bptm (pid=23291) error requesting media, TpErrno = Robot operation failed
11/09/2022 04:01:06 - Warning bptm (pid=23291) media id 000173 load operation reported an error
11/09/2022 04:01:06 - current media 000173 complete, requesting next media Any
11/09/2022 04:01:10 - Info bptm (pid=23291) EXITING with status 96 <----------
11/09/2022 04:01:10 - Info dbclient (pid=6724) done. status: 96: unable to allocate new media for backup, storage unit has none available
11/09/2022 04:01:10 - end writing
unable to allocate new media for backup, storage unit has none available (96)

磁带使用情况