Restrictions

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 the following items must not exceed 200 characters (the balance of 56 characters is used by IMS for control purposes):
    1. The length of the logical parent's concatenated key
    2. 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 these 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.