Abstract: The invention relates to the field of data processing systems and provides a method and system to enable replacement of memory modules (MU.sub.i) connected to a bus (MB) without interrupting the functioning of the system, wherein for any writing request addressed to a module to be replaced (MU.sub.i), this writing request is executed simultaneously and at the same address by the module to be replaced (MU.sub.i) and by a replacement module (MU.sub.r), and for any reading request addressed to the module to be replaced (MU.sub.i), only the module to be replaced (MU.sub.i) is authorized to execute this reading request. Next, a recopying process is started which includes sending reading and rewriting requests to a set of addresses covering the entirety of the memory space of the module to be replaced (MU.sub.i).