Choosing the number of regions

One system definition task is to specify how many BMP and message regions comprise your IMS system. The number of regions can vary depending on what your operations require.

Use the MAXREGN keyword on the IMSCTRL macro to specify a working set of BMP and message regions.

Your operations procedure stipulates how many regions are active and when they are active. The scheduling algorithm controls the actual programs that execute in the regions in response to enqueued messages. Overall throughput is conditionally based on the number of active dependent regions and the availability of shared resources for database processing. A processing program must have an available message region before it can enter the scheduling selection logic.

Up to 999 other dependent regions can be dynamically allocated by the MTO using the /START command. For DBCTL, the maximum sum of BMPs and DRA threads is 999.