Installing MRO support

CICS® multiregion operation (MRO) enables CICS regions that are running in the same z/OS® image, or in the same z/OS sysplex, to communicate with each other. MRO does not support communication between a CICS system and a non-CICS system such as IMS.

The external CICS interface (EXCI) uses a specialized form of MRO link to support communication between z/OS batch programs and CICS.

MRO does not require ACF/Communications Server or SNA networking facilities. The CICS support that enables region-to-region communication is called interregion communication (IRC). IRC is implemented in three ways:
  1. Through support in CICS terminal control management modules and by use of a CICS-supplied interregion program, DFHIRP, loaded in the z/OS link pack area. DFHIRP is invoked by a type 3 supervisory call (SVC).
  2. By z/OS cross-memory services, which you can select as an alternative to the CICS type 3 SVC mechanism. Here, DFHIRP only opens and closes the interregion links.
  3. By the cross-system coupling facility (XCF) of z/OS. XCF/MRO is required for links between CICS regions in different z/OS images of an z/OS sysplex. CICS selects XCF/MRO dynamically for such links, if available.

For information about the design and implementation of interregion communication, and about the benefits of cross-system MRO, see Introduction to CICS intercommunication.

To install support for MRO, complete the following steps:
  1. Define CICS as a z/OS subsystem. Multiregion operation with CICS requires z/OS Subsystem Interface (SSI) support. To obtain this support, you define CICS as an operating system subsystem.
  2. Install the current versions of the DFHIRP and DFHCSVC modules in the LPA.
  3. Specify appropriate system initialization parameters to enable MRO for each CICS region startup. To help you get started with MRO, a CICS job and a CICS startup procedure are supplied on the CICS distribution volume. For each MRO region, you must also create the CICS system data sets needed.

    To use cross-system MRO (XCF/MRO):

  4. Install the required sysplex hardware and software.
  5. Define the z/OS images as systems in an XCF sysplex.

    To use the MRO support:

  6. Define and install the MRO connections appropriate to your CICS environment.

Provided you complete these steps, you can use MRO to communicate with all supported levels of CICS.

If MRO is used to communicate between different releases of CICS, the function provided on any connection is that of the lower-level release.