Pending happens because the reuse days has not expired yet.  So, even if you
bring them back they would not be reused until that time passed.  Look in
the definition for the storage pool.  Based on your scenario they may have
set the reusedelay very large to prevent them from being called back.  When
the tape is pending, there is no more data on it that is not somewhere else
or has been expired.  The following excerpt is from the help q volume

PENding
     Display volumes with a status of PENDING. These are volumes from
     which all files have been deleted, but the time specified by the
     REUSEDELAY parameter from the DEFINE STGPOOL command has not
     elapsed.


The tape will go to an empty status once the reusedelay has been reached.

Paul D. Seay, Jr.
Technical Specialist
Naptheon, INC
757-688-8180