The online change function, DEDBs, and Availability of IFP and MPP Regions

In IMS systems that use ACB libraries, you can make changes to DEDBs while maintaining the availability of IFP and MPP regions that access the DEDBs by using the online change function.Changes can be made to DEDBs using online change while maintaining the availability of IFP and MPP regions that access the DEDBs. If database level changes are made to the DEDB while an IFP/MPP is running, then the application will pseudo-abend and the PSB will be rescheduled on the next DL/I call to the DEDB.

Note: The online change function is not supported and the online change commands are rejected when the IMS management of ACBs is enabled.

If database level changes are made to the DEDB while an IFP/MPP is running, then the application will pseudoabend and the PSB will be rescheduled on the next DL/I call to the DEDB.

Two level changes can be made to DEDBs. The database level changes allow:

Procedure

  1. Add or Delete DEDBs.
  2. Add or Delete segment types.
  3. Add, Change, or Delete a segment and its fields.
  4. Add, Change, or Delete segment compression routines.
  5. Add, Change, or Delete data capture exit routines.
  6. Change randomizers.
  7. Add or Delete areas.
  8. Change area RAP space allocation and the randomizer is not a 2-stage randomizer.

The area level changes allow:

  1. Change area RAP space allocation and the randomizer is a 2-stage randomizer.
  2. Change DOVF or IOVF space allocation.
  3. Change SDEP space allocation.
  4. Change CI size.

Area level changes and items 4 through 8 of the database level change require a BUILD DBD (not a BUILD PSB). In this case, with exception to items 4 and 5 when the defined PSB SENSEGs have reference to exit routines that are added or deleted, the PSB does not change. Changes can be made to DEDBs using online change while maintaining the availability of IFP and MPP regions that access the DEDBs only if there is no change to the scheduled PSB. The application will then pseudoabend with ABENDU0777 and the PSB will be rescheduled on the next DL/I call to DEDB. The message DFS2834I is issued. Other changes to the PSBs such as items 1 through 5 of the DEDB database changes, full-function database changes, or PSB changes using online change require that the IFP and MPP regions be brought down.

The following procedure describes the steps necessary to make database level changes to a DEDB with an IFP / MPP running:

  1. Use a specific user-developed application program or OEM utility to unload the DEDB through existing system definitions.
  2. DBDGEN, PSBGEN and ACBGEN to generate the application control blocks to implement the DEDB structural changes. The changed or new application control blocks must be built into the active IMS system's staging copy of ACBLIB, which is offline.
  3. Run the online change utility, DFSUOCU0, to move the changed ACBLIB from the staging ACBLIB to the inactive (A or B) copy of the ACBLIB that is online to the active IMS system.
  4. Enter the normal /DBR command sequence to remove access to the DEDB from the active IMS system. If GLOBAL option is used on /DBR, Prohibit Further Authorization flag will be set in DBRC, which will cause U0458 abend when PSB is rescheduled. Recommendation for data sharing customers who normally use GLOBAL option is to add NOPFA keyword : /DBR DB NOFPA
  5. Enter and follow the online change command sequence for PREPARE processing for ACBLIB changes.
  6. Enter and follow the online change command sequence for COMMIT/ABORT processing for ACBLIB changes. The online IMS system will switch from using the active (A or B) copy of the ACBLIB to the inactive (A or B) copy.
  7. Delete, define and initialize all of the DEDB AREA data sets with the new system definitions.
  8. Enter the normal /START DATABASE and /START AREA commands to make the DEDB and its AREAs accessible to the active IMS system.
  9. Use a specific user-developed application program or OEM utility to reload the DEDB through the change system definitions for the DEDB.
  10. On the first access to the newly changed DEDB, the application will pseudoabend and the PSB will be rescheduled. Message DFS2834I will be displayed.

    The transaction will be tried again for both IFPs and MPPs when the PSB is rescheduled. If the application attempts to access the DEDB before commit processing has completed, an 'FH' status will be returned to the application. The DEDB is inaccessible because the randomizer for the DEDB is unloaded by the /DBR command.

If either database level or area level changes are made to DEDBs while a BMP or DBCTL thread is active, then commit processing fails and the message DFS3452 is issued.