Coupling facility planning considerations

The coupling facility provides shared storage and shared storage management functions for the sysplex (for example, high speed caching, list processing, and locking functions). Applications running on z/OS® images in the sysplex define the shared structures used in the coupling facility.

The coupling facility allows applications, running on multiple z/OS images that are configured in a sysplex, to efficiently share data so that a transaction processing workload can be processed in parallel across the sysplex.

PR/SM allows you to define the coupling facility, which is a special logical partition (LP) that runs coupling facility control code. Coupling facility control code is Licensed Internal Code (LIC).

At LP activation, coupling facility control code automatically loads into the coupling facility LP from the Support Element hard disk. No initial program load (IPL) of an operating system is necessary or supported in the coupling facility LP.

Coupling facility control code runs in the coupling facility LP with minimal operator intervention. Operator activity is confined to the Operating System Messages task. PR/SM limits the hardware operator controls typically available for LPs to avoid unnecessary operator activity.

Coupling facility channel hardware provides the connectivity required for data sharing between the coupling facility and the CPCs directly attached to it. Coupling facility channels are point-to-point connections that require a unique channel definition at each end of the channel. See Coupling facility channels.

Dynamic I/O for Standalone Coupling Facility enables dynamic activation of a new or changed IODF on a standalone coupling facility CPC without requiring a re-IML or power-on reset (POR). For more information see Dynamic activation of I/O configurations for stand-alone Coupling Facilities.