Abstract: A data processing system comprising a plurality of processors each storing an instance of replicated data, the system comprising a master processor having a master memory. The master processor maintains a stored data instance in the master memory, updating the stored data instance in response to receive request messages, requesting said master processor to transmit a broadcast message to other processors. The request message contains an update of a data item updated at one of a plurality of local processors. On receipt of the request message, the master processor updates the corresponding data item in the master memory, and broadcasts the updated data item over a communications medium, eg a common bus linking all the processors, so that each local processor may update its own instance of stored data stored on the corresponding respective local memory.