| 摘要 |
PURPOSE:To hold duplexed status (service/waiting status) unvariably before and after the changing point of time from disconnection to recovery of a power supply by generating a false error signal and correcting the duplexed status when necessary. CONSTITUTION:Respective storage devices A, B have duplexed status storage parts 16, 16' including nonvolatile storage elements allowed to store false error information respectively at the disconnection of the power supply and hold the information also during the power failure. At the disconnection of the power supply, the false error information is stored in the duplexed status storage part in the waiting side storage device. If the storage device is raised as the storage device on the service side, a false error signal acting similarly to the error detecting signal is generated by the stored false error information, the storage is switched to the waiting side and the other storage device is switched to the service side to start the operation. When the storage device acting as the storage device on the waiting side immediately before the power failure is raised as the storage device on the waiting side, the operation is started as it is so that the duplexed status is held. Consequently, the status immediately before the power failure can be held.
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