z/OS Connect EE and IPIC High Availability (HA) workload balancing for CICS

The CICS service provider IPIC high availability feature provides high availability of connections, it does not provide a workload balancing mechanism. Once a z/OS Connect EE server has established a connection to a CICS region, all service requests referencing that connection will be sent to that CICS region. If the connection to the CICS region is lost, z/OS Connect will automatically connect to another CICS region listening on the shared port, providing highly available CICS connectivity. If you have a cluster of z/OS Connect EE servers and a cluster of CICS regions connected using a shared port, the connections will be balanced across the topology.

A requirement for workload balancing over IPIC connections was raised. See IBM Idea ZCEE-I-153 which corresponds to RFE 119249 "Dynamic Workload Distribution of IPIC traffic from zCEE to CICS".  This requirement was delivered by z/OS Connect Enterprise V3.0.59 (APAR PH47276).

IBM z/OS Connect is enhanced to support workload distribution of requests across a group of CICS regions, using a single connection reference. Workload distribution is configured with a new zosconnect_cicsConnectionGroup element. Groups can include other groups and the distribution of requests can be weighted.

For more details about CICS IPIC Workload Distribution, refer to the Documentation:

• CICS IPIC workload distribution for OpenAPI 3
• CICS IPIC workload distribution for OpenAPI 2 

Other possible options include:

• Use port sharing or Sysplex Distributor in front of the z/OS Connect servers to achieve workload balancing of requests

• Use IPIC HA to connect to a CICS TOR region which is part of a CICSplex using CPSM WLM for workload balancing among the available CICS AOR regions

• Use z/OS Connect policies to send work to different CICS regions. This is a fixed routing.

If you choose to use IPIC HA (option 2), keep in mind that the request coming in from z/OS Connect will be a Dynamic Program Link (DPL) request. This occurs over IPIC, and causes CICS to attach a mirror transaction in the connected CICS system. This mirror transaction must always run in this connected CICS system and is not eligible to be routed.

When z/OS Connect starts the program, CICS will start a mirror transaction to run the mirror program DFHMIRS and that will issue a EXEC CICS LINK to start the application program. This program should be defined with DYNAMSTATUS(DYNAMIC) to allow the DFHMIRS program to start the program on the target CICS application owning region (AOR). If this program is defined at NOTDYNAMIC, the program will not be routed and will run in the local system, terminal owning region (TOR), which is where DFHMIRS is running.