| 摘要 |
PURPOSE:To switch an access to two H/Ds by means of three statuses by permitting a status holding part consisting of a nonvolatile memory element to have the three statuses such as automatic backup showing a whole state/one system abnormality/under equalizing. CONSTITUTION:CPU 7 shifts the whole statuses in the status holding part 50 in accordance with the contents of the M system status and S system status. Since both M/S systems are usually normal, the whole statuses are in the state of automatic backup 60. When one of the M system or S system becomes abnormal, the state is shifted to one system abnormality 61. When applying HDC or H/D is repaired and exchanged so as to recover a function in the state of one system abnormality 61, the state is shifted to under equalizing 62. When an equalizing operation is completed, the state return to automatic backup 60. CPU 7 refers to the status holding part 50 at the time of performing access to H/Ds 20 and 21 so as to switch an object to be accessed. Thus, the normal function is rapidly and correctly recovered. |
