This error is shown when Veeam Backup & Replication does not recognize the MTF header on the tape as having been written by Veeam Backup & Replication. In such a situation, the tape was likely written by a third-party application. This error is implemented by Veeam Backup & Replication as a precautionary measure to prevent unintentional erasure of valid data stored on the tape.

If a tape library is being used, the tape that triggers the error will be placed in the "Unrecognized" media pool. In the case of a standalone tape drive, the tape will be excluded from usage altogether to ensure the preservation its data.

The 'Unknown media (possibly in use by another application)' error is itnended behavior, designed to prevent unintentional erasure of potentially valid data written by another application.

If you are transitioning from a different backup solution to Veeam Backup & Replication, it is important to carefully consider whether you want to preserve or erase the old data on the tape.

If you are certain that the tape does not contain any critical or valuable data and you want to reclaim it for Veeam Backup & Replication usage, you can utilize the Erase function to wipe the tape's header.

Note: In rare instances, brand new tapes may come preformatted from the manufacturer.