Getting started

This section introduces the Change Accumulation utility of the BMC AMI Backup and Recovery for IMS product and the CHANGE ACCUMULATION PLUS (CHAMP) product.

To facilitate recovery of a database after a hardware or software error, all changes to that database are recorded and saved in a system or recovery log data set.

Performing a recovery requires a recovery utility to process all change records since the last image copy. In some cases, this can include several hundred tapes or cartridges, resulting in a recovery that can take many hours.

To reduce this lengthy recovery time, you can perform the process of change accumulation on one or more databases (called a change accumulation group). This change accumulation process consolidates all of the change records for a particular database block or record into a single change accumulation record. These consolidated records are written to the change accumulation data set where they can be used as input to the recovery utility. Using the change accumulation data set instead of the original log records normally reduces recovery time significantly. As a result, many installations find that the overhead of running change accumulation on a regular basis, or prior to recovery, is cost-effective for improving recovery time and critical database availability.

Problem

The IBM IMS Database Change Accumulation utility (program name DFSUCUM0) is I/O intensive, requires significant resources for sorting change records, and can sometimes take hours to complete the run. To process multiple change accumulation groups, you must run this utility once for each group--the same logs are processed independently for each group processed. Many installations have determined that change accumulation takes too long to process, is inflexible, and consumes too many resources. Although most database administrators prefer to use change accumulation on most databases, some don’t use it at all, some use it on only their most critical databases, and some use it only when a recovery is to be done.

Solution

The BMC Change Accumulation utility exploits high-end processors with multiple engines, large memories, and high-speed channels and controllers.

It uses a multiple task control block (TCB) architecture intended to minimize both elapsed and CPU time by overlapping as much processing as possible. It also offers many customization options that you should consider when evaluating and implementing the utility in your environment.

The Change Accumulation utility satisfies a critical need for a faster, flexible, and more efficient way to accumulate database changes and ready them for a recovery process. It supports both full-function and data entry databases (DEDBs). Additionally, you can invoke an Incremental Image Copy function in the Change Accumulation utility if you have installed the BMC Image Copy utility, which is available with the BMC AMI Backup and Recovery for IMS product and the IMAGE COPY PLUS product.

This section contains the following topics: