Internal Coupling Facility (ICF)

You can purchase and install one or more ICF features for use in coupling facility LPs. With this feature, the coupling facility runs on special ICF processors that no customer software can use. This feature allows the coupling facility function to be performed on the CPC without affecting the model group and thus without impacting software licensing costs for the CP resources used by the coupling facility. See Considerations for coupling facilities using Internal Coupling Facility (ICF) processors.

These features are ordered separately, and are distinguished at the hardware level from any general-purpose CPs, Integrated Features for Linux® (IFLs), Integrated Information Processor (zIIPs). ICFs, IFLs, and zIIPs are perceived by the system as multiple resource pools.

CFCC code is now applied using non-disruptive microcode apply as part of the MCL apply sequence.

Coupling facilities that reside on the same CPC as one or more z/OS® parallel sysplex logical partitions are ideal for coupling resource sharing sysplexes (sysplexes that are not in production data sharing with IMS, DB2® or VSAM/RLS). You can simplify systems management by using XCF structures instead of FICON FC connections.

It is not recommended to use of coupling facilities that reside on the same CPC as one or more z/OS parallel sysplex logical partitions involved in data sharing that are in the same sysplex unless using System-Managed CF Structure Duplexing or Asynchronous Duplexing for Lock Structures for all relevant data sharing structures. This is because of the possibility of double outages involving the simultaneous loss of a coupling facility image and one or more z/OS system images that are using the coupling facility for data sharing. Depending on the structure, a double outage can result in a significantly more involved recovery than a single outage of either a coupling facility or a z/OS image in isolation from one another. With System-Managed CF Structure Duplexing or Asynchronous Duplexing for Lock Structures for all relevant data sharing structures, it is possible to have a production data sharing configuration with a coupling facility image and one or more z/OS system images in the same sysplex on a single CPC. This is because duplexing provides the necessary failure isolation solution.

With the use of System-Managed CF Structure Duplexing for all relevant data sharing structures, it is possible to have a production data-sharing configuration that uses only 2 or more internal CFs, because duplexing avoids the "single point of failure" failure-isolation issue.

ICFs on stand-alone coupling facilities need configuration planning to account for storage and channels. The storage requirements for the CPC with an ICF installed likely increases, especially if software uses the coupling facility to provide additional function not available except when running a coupling facility in a parallel sysplex. For more information, see Dynamic activation of I/O configurations for stand-alone Coupling Facilities .