Abstract: A method and apparatus for serializing a request for access to a resource originating from a requester in a system of a multisystem complex. Each system of the complex maintains local contention data indicating contention between requesters on that system for access to the resource, as well as a local contention summary summarizing the local contention data. A global manager for managing contention between the systems uses the local contention summaries to determine the existence of global contention for the resource. In response to a request for access to the resource originating from a requester on a system, the system determines whether the request requires an update of the local contention summary for the system. If the request does not require an update of the local contention summary, the system processes the request in accordance with the local contention data for the system.