Advanced Topics › Coupling Facility Structure Control Files (XES)

Coupling Facility Structure Control Files (XES)

A coupling facility list 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. To use a coupling facility list structure for communication, all CA MIM systems must reside in the same sysplex.

Coupling facility list structures must be predefined. Define coupling facility structure control files in the Coupling Facility Resource Management (CFRM) policy couple data set:

• Allocate and format the CFRM couple data set using the IBM utility IXCL1DSU, if one is not already in use in the parallel sysplex.
• Update the policy information in the CFRM couple data set using the IBM utility IXCMIAPU.
• Activate the coupling facility policies using the following z/OS operator command:

  SETXCF START,POLICY
  

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

You can identify coupling facility structure control files using the following methods:

• Using the ALLOCATE statements in the MIMINIT member of the CAI.CBTDPARM data set
• Dynamically issuing the ALLOCATE command

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. However, instead of a physical hardware reserve, the list header lock is used to serialize cross-system access to the list structure.