VERIFICATION SYSTEM FOR OPERATION COINCIDENCE AT DUPLEX CPU MAINTENANCE EXCHANGING TIME

PURPOSE: To prevent a fault due to an initial defect that a CPU has from causing a system shutdown by extending to both CPUs when the CPU having the initial defect is incorporated in the system wherein while one CPU is in operation, the other CPU can be maintained and exchanged. CONSTITUTION: This system is provided with duplex system state storage means 110 which stores the respective states of both-system identical operations, both-system nonidentical operations, and both-system operation coincidence verification and an operation comparing means 110 which compares the operations of both the systems only when the storage means 110 is in the both-system operation coincidence verification state. After maintained and replaced CPU incorporation, the identical operations of both the systems are started, the storage means 110 is changed from the both-system nonidentical operation state to the both-system operation coincidence verification state, and a comparison between the operations of both the systems by the operation comparing means 120 is started; when the comparison result of the operation comparing means 120 shows a coincidence, the storage means 110 is placed in the both-system identical operation state, but when not, the storage means is in the both-system nonidentical operation state, thus monitoring the state.