Hidden, to some managers running HP 3000s, is the VSTORE command of MPE/iX to employ in system backup verification. It's good standard practice to include VSTORE in every backup job's command process. If your MPE references come from Google searches instead of reading your NewsWire, you might find it a bit harder to locate HP's documentation for VSTORE. You won't find what you'd expect inside a MPE/iX 7.5 manual. HP introduced VSTORE in MPE/iX 5.0, so that edition of the manual is where its details reside.
For your illumination, here's some tips from Brian Edminster, HP 3000 and MPE consultant at Applied Technologies and the curator of the MPE Open Source repository, MPE-OpenSource.org.
If possible, do your VSTOREs on a different (but compatible model) of tape drive than the one the tape was created on. Why? DDS tape drives (especially DDS-2 and DDS-3 models) slowly go out of alignment as they wear.
In other words, it's possible to write a backup tape, and have it successfully VSTORE on the same drive. But if you have to take that same tape to a different server with a new and in-alignment drive, you could have it not be readable! Trust me on this -- I've had it happen.
If you'll only ever need to read tapes on the same drive as you wrote them, you're still not safe. What happens if you write a tape on a worn drive, have the drive fail at some later date -- and that replacement drive cannot read old backup tapes? Yikes!
Unfortunately, SLTs have to be written to tape (at least, for non-emulated HP 3000s). However, your drive will last years longer if you only write to it a few times a year.