In a star complex, global resource serialization uses a XES lock structure to serialize requests for global resources.

Figure 1 shows an example overview of a three system star complex. All systems in a star complex must be members of the same sysplex and be connected to a coupling facility containing the global resource serialization lock structure, ISGLOCK, to manage contention for global resources. For practical purposes, where global resource serialization star complex is concerned, the terms sysplex and complex are synonymous. No channel-to-channel (CTC) connection of systems, other than those managed by XCF, are supported by global resource serialization in a star complex.

Figure 1. Overview of the global resource serialization star complex

The ISGLOCK Lock Structure: When a system in a star complex issues an ENQ, DEQ, ISGENQ, or RESERVE request for a global resource, global resource serialization converts the request to a lock request against the ISGLOCK lock structure. Global resource serialization uses the ISGLOCK lock structure to coordinate the requests to ensure proper resource serialization across all systems in the complex. The status of each request is returned to the system that originated the request. Based on the results of these lock requests, global resource serialization will respond to the requester with the outcome of the serialization request.