摘要:
In the master control unit, updated information is transferred to a slave control unit and a coherence of information between the master control unit and the slave control unit is periodically checked, thereby eliminating a difference of the internal information of the two units which execute a control, a status monitor, and a maintenance of a computer system in an on-line manner and guaranteeing the coherence. When the master control unit recognizes a difference between the information for a predetermined time or more, the slave control unit is halted and the information of the master control unit is made effective. With respect to an abnormality of the master control unit, the master control unit halts by itself. In this instance, the slave control unit is shifted to the master status and takes over the process.