To be more specific then, the situation in question is that VMBACKUP sends
a VMBMNT command to the tape operator (sysoper in this case). Sysoper is
running programmable operator so the command triggers a DFSMSRM MOUNT
command to RMSMASTR:
address command 'DFSMSRM MOUNT VOL 'volid' (LIBNAME 'libn' READWR',
'ATTACH VMBACKUP VDEV' addr
That will set the "assignment" latch, if I understand it, since the
NOASSIGN option is not used. I can see, in the consoles that RMSMASTR
attaches the drive to itself to mount the volume, detaches it, and attaches
it to VMBACKUP. When VMBACKUP completes, I can see the VMBRAM0620 detach
message. In this situation, where the default "ASSIGN" is issued to
RMSMASTR and then the drive is ATTACHed to VMBACKUP and DETACHed, should or
would the "assignment" latch ever be left set? MVS is not involved as far
as being a guest under CP. The MVS in question is a separate system
running in it's own LPAR.
Jim
At 12:48 PM 5/15/2006, you wrote:
It depends. The latch you are talking about is called "assignment". You
can attach a drive to a guest WITH ASSIGN (the default) or WITH NOASSIGN.
If the guest handles assignments itself (e.g. a guest OS), then NOASSIGN
is useful. CMS does not natively perform assignment, so you typically use
WITH ASSIGN for a CMS user.
When MVS assigns the drive to itself depends on the configuration and the
subsystem. You can assign at vary online time, or you can delay to
allocate time, or you can let the job do it itself. JES2 and JES3
capabilities differ. Many customers use CA's MIM, which handles the
assignment itself (or doesn't use ASSIGN at all, depending on the config).
There are some other latching mechanisms available as well, but they don't
work with z/VM.
QUERY TAPE ACTIVE shows you tape drives that are ATTACHed or in use by CP
(e.g. SPXTAPE). If not active, then QUERY TAPE FREE shows those that are
available, though a FREE tape may be assigned to another system at the
moment. Now, it is possible if you ATTACH NOASSIGN, and you then DETACH
the drive while the guest has the drive assigned to the VM system, CP does
NOT release the assignment. The VM system still owns the drive but it
will appear as FREE. You will have to VARY OFF said drive to release the
assignment.
Alan Altmark
z/VM Development
IBM Endicott
Jim Bohnsack
Cornell Univ.
(607) 255-1760
