CA Dynam for VSE User Guide

Modifying Logical Unit Assignments (LUBS)
When CA Dynam/D controls the file, logical unit assignments given in the JCL
are checked to ensure that they conform to these rules; they are replaced by
correct ones if they are in error. If no logical unit numbers are given in the
JCL, or if the specified ones are already either assigned to other disks or have
been replaced as described above, then dynamic LUB allocation is invoked.
When a sufficiently long consecutive series of available SYS numbers is found,
it is allocated to the file.
Modifying Logical Unit Assignments (LUBS)
Dynamic LUB Allocation
The Dynamic LUB Allocation facility enables you to define ranges of LUBs for
use by CA Dynam/D, whenever an assignment needs to be modified. In order
to use this facility, the COMLUB option record must be defined. For more
information about the use of the COMLUB option record, see the Programming
Guide.
This facility ensures that disk files will not be cross-assigned. For example, if a
program opens two files simultaneously on separate disk volumes with the
same SYS number, CA Dynam/D will use the specified logical unit for the first
file, and will choose another logical unit for the second file from a user-defined
range.
Thus, the two files will have unique SYS numbers pointing to different disk
volumes. This eliminates the danger of cross-assignment.
Defining LUB Ranges
You can define a range of LUB entries for CA Dynam/D to use, or even a series
of LUB entries. For example, you can define ranges SYS030 through SYS039,
SYS050 through SYS052, and SYS058 through SYS070 as available LUB
entries.
CA Dynam/D uses dynamic LUB allocation to find an available LUB or
programmer logical SYS number. The existence of the COMLUB option record
is checked whenever CA Dynam/D needs to find an available logical unit to
assign to a disk address.
In the case of multivolume DA files, CA Dynam/D uses dynamic LUB allocation
to find a consecutive series of available programmer logical SYS numbers long
enough for all the volumes used by the file. If you work with this type of file
under CA Dynam/D control you should be sure that the LUB entry ranges
defined in your COMLUB option record include plenty of room in the form of
consecutive series.
Chapter 4: Disk File Management 4–27