You didn't say how your 3494 is partitioned, but it sounds like you don't
have unique tape category codes defined for each server sharing the 3494,
to keep them from trying to use each other's tapes; or some tapes were
manually defined as volumes to multiple servers instead of being picked up as
scratches.  Do 'q libr' on each server to check your category codes.   Make
sure you don't have a server's library definition in another server.  Review
your Checkin to assure that tapes are going to the right assignments.
Use the mtlib command to review the category codes of all tapes, and compare
to ADSM's libvol conceptions as to what volumes each server thinks it has.
       Richard Sims, BU