Patent ID: 7751310

Claim:
A fault tolerant duplex computer system in which two systems perform duplex running in synchronization while monitoring mutual operation situations, comprising: a data processing section which causes each system to repair and announce a trouble generated in a process of transferring data or executing an arithmetic operation therein; a fault diagnosis processor which announces information of the trouble generated in the system and executes processing instructed to the system; and a fault monitoring section which classifies pieces of trouble information received from the systems to record them as reparable trouble information or irreparable trouble information, and instructs trouble repairing processing to the systems based on the information, wherein the fault monitoring section updates the reparable trouble information of a relevant system when a reparable trouble is received from each system; updates the irreparable trouble information of a relevant system to instruct a diagnosis of the system when an irreparable trouble is received; and compares the pieces of trouble information from the systems with each other when an out-of-sync situation is received, to instruct synchronous processing by setting the system including a smaller amount of the trouble information as an active system and the system including a larger amount of the trouble information as a standby system.