Checking XCF/XES connectivity and performance

In both ring and star complexes, XCF and XES connectivity are critical to global resource serialization function. If either are not well tuned, the performance of the allocation of global resource requests will suffer. If your installation is running a global resource serialization ring complex, see to ensure optimal tuning of the sysplex.

In a global resource serialization star complex, you should apply appropriate resource to the coupling facility where you have allocated the ISGLOCK structure. Make sure that the structure is large enough to minimize false contention and that the coupling facility containing the ISGLOCK structure is fast enough to satisfy lock requests from the z/OS images. If you do not, you could see the following problems with your global resource serialization complex:

Symptom	Likely causes
Excessive processor utilization in the global resource serialization address space	The CF with the ISGLOCK structure is using shared CPs. The CF with the ISGLOCK structure is of an older technology than the z/OS system. High contention for global resource serialization managed resources.
Long ENQ response times	The CF does not have enough paths to handle the incoming requests. The ISGLOCK structure is too small, causing high false contention rates. The CF with the ISGLOCK structure is using shared CPs. The CF with the ISGLOCK structure is of an older technology than the z/OS system.
ENQ requests suspended	The ISGLOCK structure is being rebuilt. There are hung requests to the ISGLOCK structure. A system in the sysplex is not responding to XES requests.

The Coupling Facility Structure Sizer Tool (CFSIZER) is a web based application that will return the structure sizes based on the latest CFLEVEL for the IBM® products that exploit the Coupling Facility. See z/OS Internet Library.