Help with Arcserve Backup

Hello I need to restore some backups from a DAT 72 tape drive and it sees all the tapes as blank, the media pools have also vanished from the Arcserve server, is there anything I can do to recover them?

What is the best way to keep backup tapes and how long do they last?

Hope to hear from you.

I run Brighstor Arcserve 9 on a Windows 2000 Server HP Proliant ML 370 G3