A data processing system includes a host and a plurality of locations. A difference recording operation between a first location of the plurality of locations and a second location of the plurality of locations is started. A first operational relationship between a third location of the plurality of locations and the first location is started. A signal is sent in response to the first operational relationship starting after the difference recording operation. A first dataset is updated in response to the host writing data to at least one of the first location or the second location. The first dataset is updated with changes to the first location in response to the signal.