>If a tape is already mounted, just because it is mounted doesn't mean it
>isn't in the 3494's inventory...

Indeed.  To visually appreciate this, go to the 3494 Operator Station and pull
down the Database menu.  It can display all volumes, and tell you what's going
on with them.  You can also query remotely, as in...

Volume attributes                       3494 library codes, reported as
                                        numerical values in the 2nd column of
                                        volser report 'mtlib -l /dev/lmcp0 -qI',
                                        or interpreted by the detailed report
                                        'mtlib -l /dev/lmcp0 -vqI'.
                                        Codes and meanings are defined in the
                                        /usr/include/sys/mtlibio.h header:
                                         80  Volume present in library, but not
                                             accessible. (Tape probably stuck in
                                             drive - Int Req situation.)
                                         40  Volume present in library, is
                                             currently mounted.
                                         20  Eject pending.
                                         10  Ejection underway.
                                         08  Misplaced - missing.
                                         04  Unreadable label or unlabeled.
                                         02  Used during manual mode.
                                         01  Manually ejected.
                                         00  Volume present in library, not
                                             mounted.
                                         89  Volume not in library or misplaced
                                             in library.  Usually accompanied by
                                             Category Code FFFA, saying that the
                                             volume was Manually Ejected, as
                                             when the volume is defective and is
                                             out to be replaced.

 Richard Sims, BU