IMS™ HP Prefix Resolution
resolves and updates prefixes of IMS databases
that are involved in logical relationships as a single job step, with
certain rules and restrictions.
The following restrictions apply to IMS HP
Prefix Resolution:
- IMS HP Prefix
Resolution cannot run under IMS region
controller (DFSRRC00).
- IMS HP Prefix
Resolution cannot run under IMS Utility
Control Facility (UCF).
- The Prefix Update function does not support IMS logging.
- The Prefix Update function does not support HISAM
databases that have either an internal or an external logical relationship.
If there is a logical relationship in your HISAM database, specify
the FABYWF3O DD statement on Concurrent Prefix Update JCL or the Stand-Alone
Prefix Update JCL. The Prefix Update function writes the WF3 records
for HISAM databases into the FABYWF3O data set so that you can update
the HISAM database by using the IMS Database
Prefix Update utility with the FABYWF3O data set.
The IMS Database Prereorganization
utility (DFSURPR0) performs a limit check for logical parent/logical
child combinations affected by an intended database initial load or
reload. The limit check is a worst-case check. If the limit check
fails for a logical parent/logical child combination, message DFS885I
is issued by the IMS Database
Prereorganization utility. Refer to IMS Messages and Codes, Volume 1 for an explanation
of the message.
The limit check is the same as the one described
in IMS Database Utilities for the IMS Database Prefix Resolution utility,
and is as follows:
- For any given logical parent/logical child pair, the sum of items
1 and 2 below must not exceed 200 characters (the balance of 56 characters
is used by IMS for control purposes):
- The length of the logical parent's concatenated key
- The length of the sequence field of the logical child as seen
by its logical parent
- The sum must be computed once for the logical parent and once
for the logical child. These summations are treated separately.
- One or more of the above quantities can be omitted from the summations
as described:
- The logical parent's concatenated key length must be included
in both summation limit checks if the logical parent is being initially
loaded, or if the logical child does not point to the logical parent
with a logical parent pointer.
- The logical child's sequence field length, as seen by its
logical parent, must be included in the logical child's limit
check if the logical child is being initially loaded and if it has
a logical twin chain. Otherwise, it can be omitted.
If the listed
limit check is not satisfied for either a logical parent or a logical
child, the user can omit loading of the logical parent or logical
child at initial database load time. The logical parent or logical
child can then be inserted into the database at a later time by an
application program operating in an update mode. Once a database is
loaded, one or more of the components of the limit check can be omitted.