Advanced Topics › Communication Methods › Cross-system Communication Methods › Physical Control File Communication Methods › Coupling Facility Structure Control Files (XES)

Coupling Facility Structure Control Files (XES)

A coupling facility structure control file is a list type of structure that resides in a coupling facility. A coupling facility can be a stand-alone device, for example, a 9674, or it can be a PR/SM LPAR running the coupling facility control code. Consider the following recommendations:

• We recommend a minimum structure size of 10 MB for structure allocation.
• To use coupling facility structure control files, all members of the MIMplex must also be members of the same parallel sysplex.
• For recovery purposes, we recommend that you establish the CFRM policy so the structures are allocated on separate coupling facilities.

CA MIM uses of the IBM XES (Cross-system Extended) Services when using coupling facility control files.

A coupling facility structure control file can be used in any communication environment in which a DASD control file can be used, that is, DASDONLY or CTCDASD.

You must define coupling facility structure control files in the Coupling Facility Resource Management (CFRM) policy couple data set:

• Use the IBM utility IXCL1DSU to allocate and format the CFRM couple data set, if one is not already in use in the parallel sysplex.
• Use the IBM utility IXCMIAPU to update the policy information in the CFRM couple data set.
• Activate the coupling facility policies using the SETXCF START,POLICY z/OS operator command.

Note: For detailed information, see the IBM publication, Setting up a Sysplex.

You can identify coupling facility structure control files using ALLOCATE statements in the MIMINIT member of the MIMPARMS data set. The XESFILEID keyword and the STRNAME keyword of the ALLOCATE statement uniquely specify a control file identifier and a structure name for the control file.

From an operational standpoint, a coupling facility structure control file functions similarly to a DASD control file. CA MIM address spaces on each system of the MIMplex contend for access to the list structure. The list header lock is used to serialize cross-system access to the list structure.