CA Dynam for VSE User Guide

Selecting Logical Units
LUB Availability
Once a primary LUB is established, CA Dynam/D next checks to see if the
primary LUB is available—already assigned to the correct device, or
unassigned (UA). In either case, it will be used and no access to the COMLUB
option record for dynamic LUB (DYNLUB) processing will be made. But if the
primary LUB is already assigned to another device, then the primary is
discarded and COMLUB processing is entered to choose another acceptable
LUB.
If a COMLUB range has been established for the partition, all LUBs in the range
are searched to locate one which is available (either already assigned to the
correct device, or unassigned—UA). If no COMLUB range has been established,
all programmer LUBs in the partition are searched, beginning with the top and
working down.
SYS Number Considerations
IJSYS Files
IJSYS files are never subject to COMLUB. If an assignment for one of these
files must be made, CA Dynam/D will change the assignment instead of
choosing another logical unit.
SD Work Files
When using SD work files, CA Dynam/D searches the volume or pool specified.
If the file is found, CA Dynam/D will access it; otherwise, CA Dynam/D will
allocate it.
DA Files
VSE requires you to include a specific logical unit specification on each EXTENT
statement in the JCL for a DA file. If there are multiple extents on one volume,
the logical unit specified must be the same for each extent. When the file
spans another volume, the SYS number for the first extent on the new volume
must be one number higher than the SYS number for the preceding extent.
Further extents on the new volume must again have the same SYS number as
the first extent on that volume, and so on.
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