My colleague was putting the same Backups (but at different levels: 0,1,2) into 1 tape everyday (i.e. he replaced the tape everyday). He was doing it for quite some time now to save on tapes. When he tried to restore it to another server, it was complaining that it was an invalid archive level. The tape contained Backup Levels 0,1, and 2.

He's using IDS 7.31 on SCO Unix 5.0.5 and the tape device was pointing to /dev/rStp0

What seems to be the problem?

Thanks.

If you run a level 0 backup to a tape....then run a level 1 (or level 2) backup to the same tape....the level 1 backup will overwrite the contents on the tape - meaning your level 0 is now destroyed.

ALWAYS use different tapes for logical log backups, level 0, level 1, and level 2 backups - and label them accurately