PURPOSE: To obtain the consistency of data and to efficiently utilize master data by taking shared data out in the distributed processing of an cooperative operation, etc., without performing exclusive control, and further informing other operators of the update when the data are updated.

CONSTITUTION: When a work station 2 copies master data in the master data part 11 of a host machine 1, a common data update informing part 12 stores information showing that which master data are copied and which work station 2 the data are stored in a lock control part 13. When the copied data are updated on an optional work station 2 and the master data are updated corresponding to the update, the shared data update informing part 12 retrieves the information stored in the lock control part and informs other work stations 2, where the data to be updated are stored, of the update.