To provide a distributed common memory system and control method thereof, which can always maintain the integrity of a data structure on a distributed common memory of a standby node.

Transaction display bits are kept in memory rewriting information transferred between an active node and the standby node. The active node transfers the memory rewriting information on the occurrence of memory write. The transferred memory rewriting information is accumulated in a buffer of the standby node side. By the arrival of the rewriting information having no transaction display, the accumulated rewriting information is indivisibly written in the common memory from the processor of the standby node.