With the introduction of the Coupling Thin Interrupt support, which is used only when the CF  partition is using shared engines and the new  DYNDISP=THININTERRUPT  parameter, the CFCC  code is changed to handle these interrupts correctly. CFCC was also changed to relinquish  voluntarily control of the processor whenever it runs out of work to do. It relies on Coupling  Thin Interrupts to dispatch the image again in a timely fashion when new work (or new  signals) arrives at the CF to be processed. This capability allows ICF engines to be shared by several CF images. In this environment, it  provides faster and far more consistent CF service times. It can also provide performance that  is reasonably close to dedicated-engine CF performance if the CF engines are not CF Control  Code thin interrupts.  The introduction of thin interrupts allows a CF to run by using a shared processor while  maintaining good performance. The shared engine is allowed to be undispatched when there  is no more work, as in the past. The new thin interrupt now gets the shared processor that is  dispatched when a command or duplexing signal is presented to the shared engine. This function saves processor cycles and is an excellent option to be used by a production  backup CF or a testing environment CF. This function is activated by using the CFCC  command  DYNDISP ON . The CPs can run z/OS operating system images and CF images. For software charging  reasons, generally use only ICF processors to run CF images. Dynamic CF dispatching is shown in Figure 3-16. For more information about CF configurations, see  Coupling Facility Configuration Options ,  GF22-5042. Figure 3-16 Dynamic CF dispatching (shared CPs or shared ICF PUs) z/OS z/OS Function Setup HMC  Partition  Image Profile CF  ICF CP BACK UP C F z/OS z/OS CF  ACTIVE C F With Dynamic CF dispatching enabled, backup  CF becomes active only for new work DYNDISP ON (CFCC cmd) IMAGE Profile setup 142  IBM z14 (3906) Technical Guide