Internal Coupling Facility (ICF)

ICFs are PUs in a CPC configured to run only CFCC code. The PUs are not shipped with a fixed function assignment, but are assigned during power-on reset (POR) or later non-disruptively by on demand offerings such as: CBU, CUoD, CIU, ON/OFF CoD.


Those offerings allow the customer to convert, in seconds, a non-characterizable PU in any PU personality type such as: CPU, ICF, IFL, zAAP, zIIP and SAP.


An ICF can reduce the cost of exploiting coupling facility technology because:

  • ICFs are less expensive than CPs.
  • An ICF has a special software license charge. Special PR/SM microcode prevents the defined ICF PUs from executing non-CFCC code such as z/OS.



CBU – Capacity BackUp

CFCC – Coupling Facility Control Code

CIU – Customer Initiated Upgrade

CoD – Capacity on Demand

CP – Central Processor

CPC – Central Processor Complex

CPU – Central Processor Unit

CUoD – Capacity Upgrade on Demand

ICF – Internal Coupling Facility

IFL – Integrated Facility for Linux

POR – Power-On Reset

PR/SM – Processor Resource/System Manager

PU – Processor Units

SAP – System Assistance Processor

zAAP – z Application Assist Processor

zIIP – z Integrated Information Processor


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