A data processing system includes a memory system, a plurality of masters that issue requests for access to memory blocks within the memory system, a plurality of snoopers that provide partial responses to requests by the masters, and response logic that generates combined responses for the requests in response to the partial responses provided by the plurality of snoopers. The plurality masters includes a winning master that issues a request for a particular memory block, and the plurality of snoopers includes a protecting snooper that, in response to receipt of the request, provides a partial response and protects a transfer of coherency ownership of the particular memory block to the winning master until expiration of a protection window extension following receipt from the response logic of a combined response for the request.