Mounts were going into allocation pending and noticed that VM:Tape had drives RESERVED for VMBACKUP but no jobs were running.
There are two different methods you can use to resolve this:
Issue VMTAPE DRAIN and START commands to free the drives.
VMTAPE DRAIN raddr
VMTAPE START raddr
If multiple drives are in a RESERVE status, each command above can have a string of addresses separated by a space.
Another method is to issue VMTAPE RELEASE DRIVE * from the VMBACKUP console.