JP2879480B

PURPOSE:To quickly restart processing by switching control to a stand-by side computer when abnormality due to an operation side computer occurs and the operation side computer aborts its operation within a prescribed time after the generation of the step-out of synchronism between the operation side computer and the stand-by side computer in a system consisting of the operation side computer and the stand-by side computer. CONSTITUTION:The operation side computer system 1 for executing process control is connected to the stand-by side computer system 2 through a communication line 4 and a signal line 5 and a tracing function module 3 is connected between both the systems 1, 2. The system 1 executes process control and transfers process data to a data base 21 in the system 2 through the module 3. When a bus 13 e.g. generates abnormality, the system 2 recognizes the step- out of synchronism and starts up a timer. When the system 1 runs down, the system 2 detects the abnormality of the system 1 by the time-out or the like. When the system down is generated within a prescribed time from the step-out of synchronism, control is switched to the system 2.