Tape Backup's are not overwriting.

Hi Guys,

Nedd your help on this.. I'm new to backup exec. We are taking backups for our servers to tape. We have set OPP as 4 days and backup runs every Tuesday. So if the backup ran today means, the tape is getting overwritable after 4 days which is expected. So on next tuesday when the backup ran again, it is getting the data appended to tape even though the tape is in Overwritable state. This is causing the tape to get full and backups are failing. Kindly help me on this.

Thanks & Regards,

TV.