Upgrade to Veeam Backup & Replication v9 or newwer.
Starting with Veeam Backup & Replication v9, the media pools are now "global" and their assocaition can be changed between tape libraries.
Alternat Solution when upgrading Veeam Backup & Replication is not possible
- Remove all tapes from Catalog (This might require the Tape Device to be powered down so all media is "offline")
- Delete the Media Pools on the Offline Library
- Remove the Offline Library (Right click + Remove Library)
- Create New Media Pools on the Online Library
- Catalog the Tapes to regain the Veeam Catalog and see the information inside Veeam's UI
While this solution is cumbersome, it is the supported method as each Media Pools is directly associated with the parent Device in versions of Veeam Backup & Replication prior to v9.