Veeam periodically rescans the tape drives. This locks the drives and prevents other tape software from writing to them.
The refresh rate on the automatic rescan is too frequent if using third party tape backup software.
This registry entry is for versions greater than 18.104.22.1684.
(Please check www.veeam.com/patches.html to make sure you are on the most recent patch.)
HKLM\SOFTWARE\VeeaM\Veeam Backup and Replication
Value: 1 (decimal)
How to remove the tape library and/or tape drive from console and disable rescan:
1. Disconnect tape hardware from server (disabling drivers may be sufficient).
2. Wait until the library moves to offline in the Veeam console.
3. Remove Library from the Veeam console.
4. Add the registry entry as documented above.
5. Close console and restart Veeam Backup service.
6. Connect tape hardware to server.
7. Open the Veeam console to verify the tape library is no longer present in the backup infrastructure.