XCF for MRO
XCF is required for MRO links between CICS® regions in different z/OS® images of a sysplex.
CICS Inter Region Communication (IRC) for multiregion operation (MRO) supports the use of XCF for inter region communication between regions in the same sysplex, making it unnecessary to use VTAM® for this communication. Each CICS region is assigned to an XCF group when it logs on to IRC, even if it is not currently connected to any regions in other z/OS images. When members of a CICS XCF group that are in separate z/OS images communicate, CICS selects XCF dynamically, overriding the access method that is specified on the connection resource definition.
Starting with CICS TS 3.2, you can specify the name of the XCF group on the XCFGROUP system initialization parameter. If you do not specify XCFGROUP, the region becomes a member of the default CICS XCF group, DFHIR000. If you run different types of CICS regions in the same sysplex (test and production or development and production, for example), you might want to use separate XCF groups for the separate collections of regions. You might also want to use multiple groups if you are approaching the limit of 2047 members in an XCF group and if you can break your CICS regions into groups of regions that do not need to communicate with each other.
- Put your production regions in a separate XCF group from your development and test regions.
- Do not create more XCF groups than you need.
- Try not to move regions between XCF groups.
CICS regions can use XCF to communicate only with other CICS regions in the same XCF group. Members of different XCF groups cannot communicate using MRO even if they are in the same z/OS image.
- A low communication overhead between z/OS images, providing much better performance than using ISC links to communicate between z/OS systems.
- Easier connection resource definition than for ISC links, with no VTAM tables to update.
- High availability, by having alternative processors, and systems ready to continue the workload of a failed z/OS system or a failed CICS region.
- Easier transfer of CICS regions between z/OS systems. The simpler connection resource definition of MRO, and having no VTAM tables to update, makes it much easier to move CICS regions from one z/OS system to another. You no longer need to change the connection definitions from CICS MRO to CICS ISC (which can be done only if CICS startup on the new z/OS is a warm or cold start).