Coupling facility channels

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Coupling facility channels are channels that use fiber optic cables (CE LR and ICA SR coupling links) or internal memory bus (ICP channel paths) to provide the connectivity for data sharing between a coupling facility and the central processor complexes (CPCs) or logical partitions (LPs) directly attached to it.

The class of CHPIDs, known as peer mode channels, provide both sender and receiver capability on the same link. Peer mode links come in these varieties: ICP (TYPE=ICP), ICA SR (TYPE=CS5), and CE LR (TYPE=CL5/CL6). Each ICP, CS5, CL5, and CL6 channel can be configured as an unshared channel path to a single coupling facility or z/OS® image, or as a shared channel path among several z/OS images and one coupling facility image.

Note: The following bulleted items only describe z/OS to coupling facility connections. However, they also apply to coupling facility duplexing connections (CF to CF).

Coupling facility channels:

  • Require a point-to-point connection (direct channel attach between a CPC or LP and a coupling facility). Internal Coupling channels can only be used to connect a coupling facility and LPs on the same CPC.
  • Can be used to connect a coupling facility to other LPs on the same CPC when a coupling facility is one of multiple LPs running on a single CPC. Internal coupling channels are recommended for these connections.
  • Can be redundantly configured (two or more coupling facility channels from each CPC involved in coupling facility data sharing) to enhance availability and avoid extended recovery time. This does not apply to Internal Coupling channels.
  • Require ICP, ICA SR, or CE LR coupling links channel path definition at the coupling facility end of a coupling facility channel connection.
  • Require ICP, ICA SR, or CE LR coupling links channel path definition at the z/OS (and, for System-Managed CF Structure Duplexing, the coupling facility) end of a coupling facility channel connection.
  • Require an ICA SR (CS5), CE LR 10Gb (CL5), or CE LR 25Gb (CL6) coupling link channel path be connected to an ICA SR, CE LR 10Gb, or CE LR 25Gb coupling link. You must define the ICP channel paths in pairs and you must connect each pair. You connect an ICP channel path to an ICP channel path by specifying the CPATH keyword on the CHPID statement for every ICP channel path.