PURPOSE: To reduce the working volume of a command operation and to prevent the error of command operating work occurring by performing the unitary management of the command operations in plural data processing systems.

CONSTITUTION: A memory device 4 that can be accessed in common from the data processing systems 1A-1C is provided. When a certain data processing system executes a command required in the plural data processing systems, the command is sent to another started up data processing system, and also, command information 6 is stored in the memory device 4, and when an unstarted up data processing system is started up, the command information 6 is read in from the memory device 4. In such a way, since the unitary management of the command required by the plural data processing systems can be performed, the working volume in the command operations of the plural data processing system is reduced, and the error of the work is prevented occurring.