Coupling Facility and Coupling Facility Resource Management

A coupling facility is a shareable storage medium (not a shared storage device) that facilitates high-speed access to shared data across applications and subsystems running on the same or different MVS systems.

A coupling facility can be shared by the systems in one Sysplex only. It enables data to be shared by all users in a Sysplex while ensuring data integrity and consistency. To share data, systems in the Sysplex must be connected to the coupling facility using coupling facility channels and must have access to the coupling facility resource management (CFRM) couple dataset.

Storage in a coupling facility is divided into distinct objects called structures. Structures are used by authorized programs to implement data sharing and high-speed serialization. Structure types are cache, list and lock, each providing a specific function to the application. MVS System Logger is a set of standard services that allows an application to write to, browse in, and delete from a coupling facility structure or linear dataset.

A coupling facility is managed using the coupling facility resource management (CFRM) policy. The CFRM policy allows a user to specify how a coupling facility and its resources are to be used at the site. In a CFRM policy, a user supplies information about each coupling facility and each coupling facility structure at the site. For information on planning a CFRM policy, see the IBM manual MVS Setting Up a Sysplex.

Perform the following steps to set up a CFRM policy:

1. Format a CFRM couple dataset by using the IXCL1DSU format utility program. For more information, see the IBM manual MVS Setting Up a Sysplex.
2. Define one or more CFRM administrative policies by using the IXCMIAPU administrative data utility. For more information, see the IBM manual MVS Setting Up a Sysplex.
3. Make one of the defined CFRM policies the active administrative policy for the Sysplex. Start it by using operator command SETXCF START,POLICY,TYPE=CFRM. For more information, seethe IBM manual MVS Setting Up a Sysplex.