I wonder if it is something like...
     That tape contains a partial file from another volume that got errors
     and was marked destroyed & discarded ? ? ?
     I'm not sure what the "q content" would show in such a case.

     Now your "q content" does show that adsm doesn't think anything is on
     that tape BUT you have to  watch a "q vol blah" 'cause I've done that,
     got 0.0 back, tried to trash a volume and seen the'ol data still
     resides on tape routine.  It was due to about a .5 K file on a tape
     with a 60 GB ets capacity (due to compression) so watch out for those
     real small files ;-)

     I would try marking the volume "destroyed" first, then try the "del
     vol blah discard=yes"  Can't say for sure if I read it or just
     encountered it but I don't think ADSM lets you del w/ discard unless
     the vol (w/ data) is marked destroyed... where aix isn't your mother,
     ADSM tries to be and works at not letting you shoot yourself in the
     foot.

     later
           Dwight