Using the common work area

The CWA in a CICS region is created (optionally) during CICS initialization, exists until CICS terminates, and is not recovered on a CICS restart (warm or emergency). The ADDRESS CWA (ptr-ref) command provides direct addressability to the CWA.

A good example of how the use of long-life shared storage such as the CWA can create affinity is when one task stores data in the CWA, and a later task reads the data from it. Clearly, the task retrieving the data must run in the same target region as the task that stored the data, or it references a different storage area in a different address space. This restricts the workload balancing capability of the dynamic or distributed routing program, as shown in Figure 1.

Figure 1. Illustration of inter-transaction affinity created by use of the CWA. The dynamic routing program needs to be aware of this CWA affinity, and ensure that it routes TRN2 to the same target region as TRN1.

CWA

However, if the CWA contains read-only data, and this data is replicated in more than one target region, it is possible to use the CWA and continue to have the full benefits of dynamic routing. For example, you can run a program during the post-initialization phase of CICS startup (a PLTPI program) that loads the CWA with read-only data in each of a number of selected target regions. In this way, all transactions routed to target regions loaded with the same CWA data have equal access to the data, regardless of which of the target regions to which the transactions are routed. With CICS subsystem storage protection, you can ensure the read-only integrity of the CWA data by requesting the CWA from CICS-key storage, and define all the programs that read the CWA to execute in user key.