Selecting the type of reorganization

BMC AMI Fast Path Online Reorg for IMS reorganizes a DEDB without taking it offline from IMS. Only the UOW that is being reorganized is held exclusively, and it is inaccessible to applications only during the time that it is being reorganized.

Because BMC AMI Fast Path Online Reorg for IMS incorporates all batch functionality that is provided by the Fast Path Reorg/EP product, you can also perform offline reorganizations by using BMC AMI Fast Path Online Reorg for IMS. For more information, see Fast Path Offline Suite documentation.

Online reorganization

The online reorganization process reorganizes a DEDB without taking it offline. Only the UOW that is being reorganized is held exclusively, and it is inaccessible to applications only during the time that it is being reorganized. Performing an online reorganization requires a license for BMC AMI Fast Path Online Reorg for IMS.

Control statement

The PFPSYSIN control statements include the command set necessary to run the online reorganization function.

A sample control statement for an online reorganization is shown in the following figure. Reorganization is limited to only the area that is specified with the IAREA keyword.

//PFP      EXEC PGM=DFSRRC00,REGION=0M,
//         PARM=(IFP,<dbdname>,DBF#FPU0)
//STEPLIB DD   DSN=BMC.PFP.LOAD,DISP=SHR
//         DD   DSN=IMS.RESLIB,DISP=SHR
//PFPSYSIN DD   *
  REORGANIZE DBD=<dbdname>,IAREA=<areaname>
/*

Performance considerations

This section discusses performance considerations for online reorganization function.

UOW locking

The online reorganization function locks UOWs one at a time while they are being reorganized. UOWs that are selected for reorganization are locked with exclusive access (EX). UOWs that are not selected for reorganization, but are needed for analysis or image copy processing, are locked with shared access (SH).

IMS/VS logging

When a UOW has been reorganized, the lock is released and the reorganization function logs the UOW updates to the IMS/VS log.

Buffer usage

The online reorganization function automatically determines the number of buffers that will be required before reorganization. Automatic determination of buffer requirements is an advantage over other reorganization utilities. Other utilities require the user to estimate the number of buffers that are required before reorganization and will fail if the estimate is insufficient.

If you want to allocate and limit the number of buffers used by the online reorganization function because of extended common storage area (ECSA) considerations, use the SELECT_UOW keyword. For more information about using the SELECT_UOW keyword, see Selectively-specifying-UOWs-for-reorganization and Fast Path/EP reference information.

Analyzing the area while reorganizing

If you have a license for the BMC AMI Fast Path Online Analyzer for IMS product, the product performs quick (checksum) pointer validation by default during the online reorganization function. The I/O that is required to read the UOW and IOVF control intervals is shared between the two functions.

Because the reorganization process does not normally access SDEP control intervals, additional I/O is required to read these control intervals if you request SDEP pointer validation. This I/O, however, is shared with the image copy function.

For more information, see Analyzing-the-DEDB-during-reorganization. For example, you can control the level of pointer validation or turn pointer validation off, depending on your performance considerations.

Creating an output image copy while reorganizing

If you create one or more output image copies while performing an online reorganization, the I/O that is required to read the UOW control intervals is shared between the two functions. A license for the BMC AMI Fast Path Online Image Copy for IMS product is required.

Unlike the reorganization process, the image copy process requires the IOVF control intervals to be processed sequentially. The I/O that is required to read the IOVF control intervals for the image copy is not shared. The I/O that is required for processing of the SDEP control intervals is shared between image copy and analysis functions.

You can use the IC subcommand to request creation of an image copy for each area during the reorganization. DBRC is informed (NOTIFY.IC) that a concurrent image copy has been created.

Message suppression

For each anomaly that is encountered in an area, the reorganization function generates a message with a specific suffix (severity) level. When the number of places that a particular condition exists is large, a large number of messages is produced. You can reduce the number of repetitious messages produced by using the MESSAGE_SUPPRESSION keyword to specify the maximum number of times that an informational, warning, error, or critical message is to be produced.

For the online reorganization process, this keyword functions in the same manner as it does for the Fast Path/EP online analysis process. For more information, see Suppressing-repetitious-messages.

Shutting down the reorganization function

When you are running an online reorganization, you can terminate the reorganization function before completion. Use the /STOP REGION regid IMS command.

Because the reorganization function reorganizes one UOW at a time, reorganization that has already been performed does not have to be repeated if the reorganization function is interrupted. UOWs that have already been reorganized remain reorganized. After restart, the reorganization function begins processing at the next disorganized UOW. Special restart JCL is not required.

MADS considerations

BMC AMI Fast Path Online Reorg for IMS fully supports multiple area data sets (MADS) for online reorganizations. All online MADS that are registered for each area are reorganized simultaneously.