Set 1 will be kept until a job overwrites the tape. An append adds to the tape without destroying exisiting data on the tape.
Exactly which job overwrites the tape is affected by a lot of other settings including:
- the media protection settings for the server
- whether the job is set to overwrite or append at the start (or append and overwrite of no appendabe tapes available)
- whether the job has filled a tape and asked for another one
- the append settings for the media set the tape is a member of
- the overwrite settings for the media set the tape is a member of
- the media set that the job is configured to use
- other available online tapes that meet the job configuration settings
- whether or not partitions are in use.
Backup Exec can only append to a tape where the media set the tape is a member of matches the media set configured in the job (and where the job starts as append). You can see how the order in which Backup Exec selects media when it neess to overwrite by looking at the tape handling section of the admin guide
