DB2 & IMS

Also, when defining the IMS transa c t i o n s RRS ma n a g e s , s p e c i f y SCHDTYP=PARALLEL and PARLIM=0 in the IMS TRANSACT macro so different transactions of the same type can be simultaneously processed in multiple dependent regions.

Process Multiple Transactions of a Global Transaction on One IMS System

A global transaction can contain multiple IMS transactions with the same IMS transaction code. Due to restrictions related to the transfer of database locks and buffers, all the IMS transactions contained in a global transaction must run in one IMS system.

Minimize the Impact on Performance of Offloading Log Data to Disk

RRS logs many activities related to the RRS events and services. The RRS data is written to a log stream. When the storage used for the log stream reaches a user-defined high threshold, a percentage of the total storage used, the z/OS system logger offloads the data to disk. The system logger offloads only enough data to bring the total storage used down to the low threshold and then stops offloading.

Correctly setting the high and low thresholds for offloading can minimize the performance impact of offloading. The threshold specifications are set in the z/OS LOGR policy stored in the z/OS LOGR couple data set. Setting the high threshold too low or the low threshold too high can result in offloading too frequently, which can slow performance. On the other hand, setting the high threshold too high could lead to the log stream storage becoming full before the system logger can offload to create more space. If a coupling facility or staging data set space for a log stream becomes completely full, the system logger rejects all write requests until the log data can be offloaded to disk.

Also, if you’re using a coupling facility log stream, determining the optimum size of the coupling facility structure helps in handling the offload processing rate and in keeping more log data available on the coupling facility.

If you’re using a disk-only log stream, the size of the staging data set is another factor affecting RRS performance. Make the size of the staging data set large enough to hold all the log data in the coupling facility.

Finally, consider not using the RRS archive log stream, which will reduce the RRS logging activities.

Diagnosing Problems Related to RRS and IMS Connect

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