Certain events in a region can be accumulated in a batch prior to posting, until the number specified in the MROBTCH system initialization parameter is reached (or ICV times out). Then, the region is started so that it can process the requests. The batching of MRO requests includes some non-MRO events such as:
Strictly speaking, batching is applicable to a TCB rather than the region. MROBTCH is applied only to the ‘quasi-reentrant’ mode TCB.
Compared to no batching (MROBTCH=1, that is, the default), setting MROBTCH=n has the following effects:
Setting MROBTCH higher than 6 is not recommended as the decreasing additional processor saving is unlikely to be worth the further increased response time.
You require a relatively low value of MROBTCH for ICV to maintain reasonable response time during periods of low utilization.
Depending on the amount of response time degradation you can afford, you can set MROBTCH to different values using either CEMT or EXEC CICS® SET SYSTEM MROBATCH(value).
The recommendation is to use CEMT or EXEC CICS INQUIRE SYSTEM MROBATCH(value) to arrive at a suitable batch value for a given workload. See the CICS Supplied Transactions for more information about CEMT; for programming information about the EXEC CICS system programming commands, see the CICS System Programming Reference manual.
During slow periods the ICV unconditionally dispatches the region, even if the batch is not complete and provides a minimum delay. In this case, set ICV to 500 milliseconds in each region.