Reusing tapes with Backup Express---Solution---
When a backup job is written to a tape, the job has retention period, which defines how long it will remain an active job in the catalog. While using Backup Express, numerous tapes are used and have different backup jobs written on them.
A tape is recycled back into the free tape rotation after all the jobs on a tape have expired out of the catalog, and after a catalog condense has been run. This last point is very important. A tape will not be marked as Free/Empty until the catalog condense has been run, even if the job on it expired days, or weeks, ago.
When the tapes are recycled back into rotation, a format is not run. BEX recognizes that the volser for that tape has been marked as empty again. When a backup job needs a tape, it puts this tape into a tape drive and then writes over what was on it.
Note that Backup Express jobs have 3 components: Base, Incremental and Differential. You need to make sure that the the retention period for all 3 components of the job is what you want it to be to make sure a tape expires at the right time.