In a data processing system, a plurality of agents communicate operations therebetween. Each operation includes a request and a combined response representing a system-wide response to the request. Within data storage in the data processing system, a data structure indicates a duration of a protection window extension for each of the plurality of agents. Each protection window extension is a period following receipt of a combined response during which an associated one of the plurality of agents protects transfer of coherency ownership of a data granule between agents. Each of the plurality of agents is configured with a duration of a protection window extension by reference to the data structure, and at least two of the agents have protection window extensions of differing durations. The plurality of agents thereafter employ the configured protection window extensions.