Tape Mounts on VM Server

   Unlike other operating systems, VM still uses an antiquated method
for mounting tapes. Some vendors have improved this with the
help of a service machine. Others have systems which allow VM
systems to share tape drives with MVS. In my case, we use both.
   When the VM ADSM server needs a tape, he autologs the tapemount
exit machine. It is the job of this machine to acquire a drive,
check the mounted volume, and then give the unit to DSMSERV. In the
vanilla environment, this probably works well. In our case, the
exit machine issues a VMTAPE (Sterling Software) 'Mount' command for
the tape and waits for the mount to complete. VMTAPE processing
calls MIA/VM (Legent) acquires a unit from the pool shared with
MVS. Once the drive is acquired, VMTAPE then calls for the requested
volume. Once the correct volume and mode has been checked, VMTAPE
hands over the unit to DSMSERV and command completion occurs on
the exit machine. Once command completion occurs on the exit
machine, I check the return code from VMTAPE and additionally
check that the mount was successful (vcuu is attached to DSMSERV).
This processing takes from 1-10 minutes. Normally this is fine.
Since the beginning, the server would occasionally mark the
Exit Machine 'Offline'. I thought it was MY problem and
tweaked the Exit Machine 'Exec'. Recently It started occuring
a bit more frequently.
   I have discovered that there are cases where the server
has the need to mount more than one tape. We only use one
Exit machine. The server will wait until the Mount is detected
and then try to autolog the service machine again for the
next mount. If this process fails 3 times, the exit machine is
marked 'Offline'. The server tries 3 times in less than 1 second.
If the Exit Machine has not completed processing or logging off,
It is marked 'Offline'. This is unacceptable. Since the Server
is using a REXX based Exit Machine, a reasonable (or preferably
selectable) period of time elapse BEFORE the Server attempts
to autolog the exit machine again. This time period should
elapse BEFORE each attempt at autologging. This would allow any
Post-Mount processing in the exit machine to complete and Logoff.
I have been reduced to constantly monitoring the ADSM server
to make sure everything is fine.

    I NEED A FIX AND I NEED IT NOW!!!

   I also need a mechanism to tell the ADSM server 'Sorry, No
Tape Drives available now, Try again later.'.


TIA,

Greg Piney
Sr. Systems Engineer
McGraw-Hill Inc.