Cross-system multiregion operation (XCF/MRO)

XCF2 is part of the MVS/ESA base control program, providing high performance communication links between MVS images that are linked in a sysplex (systems complex) by channel-to-channel links, ESCON® channels, or coupling facility links3. The IRC provides an XCF access method that makes it unnecessary to use VTAM® to communicate between MVS images within the same MVS sysplex. Using XCF services, CICS regions join a single XCF group called DFHIR000. Members of the CICS XCF group that are in different MVS images select the XCF access method dynamically when they wish to talk to each other, overriding the access method specified on the connection resource definition. The use of the MVS cross-system coupling facility enables MRO to function between MVS images in a sysplex environment, supporting all the usual MRO operations, 4 such as:

CICS regions linked by XCF/MRO can be at different release levels; see Multiregion operation. Depending on the versions of CICS installed in the MVS images participating in XCF/MRO, the versions of DFHIRP installed in the link pack areas of the MVS images can be different. If a single MVS image contains different releases of CICS, all using XCF/MRO to communicate with regions in other images in the sysplex, the DFHIRP module in the MVS LPA should be that from the most current CICS release in the image, or higher. For full details of software and hardware requirements for XCF/MRO, see Requirements for XCF/MRO.

CICS MRO in an XCF sysplex environment is illustrated in Figure 2.

Figure 2. A sysplex (SYSPLEX1) comprising two MVS images (MVS1 and MVS2). In this illustration, the members of the CICS group, DFHIR000, are capable of communicating via XCF/MRO links across the MVS images.

In MVS1, the DFHIRP module in the LPA should be at the level of the highest CICS TS z/OS release in the image.

Because it contains only CICS TS OS/390, Version 1 Release 3 regions, the DFHIRP module in the LPA can be at the CICS TS OS/390, Version 1 Release 3 level, or later.

 The picture shows a sysplex consisting of two MVS images, MVS1 and MVS2. MVS1 is z/OS. It contains two CICS TS z/OS regions and uses the CICS TS z/OS version of DFHIRP. MVS2 is MVS/ESA 5.1. It contains two CICS TS OS/390, Version 1 Release 3 regions and uses the CICS TS OS/390, Version 1 Release 3 version of DFHIRP.

In Figure 2, the MRO links between CICS1 and CICS2, and between CICS3 and CICS4, use either the IRC or XM access methods, as defined for the link. The MRO links between CICS regions on MVS1 and the CICS regions on MVS2 use the XCF method, which is selected by CICS dynamically.

Benefits of XCF/MRO

Some of the benefits of cross-system MRO using XCF links are:

Related concepts
Overview of MRO
Facilities available through MRO
Applications of multiregion operation
Conversion from single-region system
Intersystem communication
Related tasks
Steps to install MRO
Further steps
Defining links for multiregion operation
Related reference
Requirements for XCF/MRO

2.
XCF. The MVS/ESA cross-system coupling facility that provides MVS™ coupling services. XCF services allow authorized programs in a multisystem environment to communicate (send and receive data) with programs in the same, or another, MVS image. Multisystem applications can use the services of XCF, including MVS components and application subsystems (such as CICS®), to communicate across a sysplex. See the MVS/ESA Setting Up a Sysplex manual, GC28-1449, for more information about the use of XCF in a sysplex.
3.
Coupling facility links. High-bandwidth fiber optic links that provide the high-speed connectivity required for data sharing between a coupling facility and the central processor complexes attached to it.
4.
XCF/MRO does not support shared data tables. Shared access to a data table, across two or more CICS regions, requires the regions to be in the same MVS image. To access a data table in a different MVS image, you can use function shipping.

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