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

Question & Answer


How can I balance the z/OS Connect Enterprise Edition (EE) workload over an IPIC connection coming into CICS Transaction Server for z/OS (CICS TS)? I have set up IPIC High Availability (IPIC HA) in 4 CICS regions and performed a load test. The work is being processed but only in one of the regions.


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 has been raised and might be added in the future. The request for enhancement (RFE) is 119249: Dynamic Workload Distribution of IPIC traffic from zCEE to CICS. To increase the chances of this enhancement request being completed you can click on the RFE, sign on using your IBMid, scroll to the bottom of the page, and click on "vote" to vote for it.

In the meantime, the following are three ways to work around this problem:

  • Have a z/OS Connect server in each CICS region and 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 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.

Shayla Robinson
CICS/CPSM/zOS Connect L2 Support

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Modified date:
13 February 2019