Among existing information systems (server system etc.), there exists, as illustrated in FIG. 13, an information system including one or more (in the figure, two) system boards, multiple I/O boards, and a configuration controller board.
The system board in this information system is a board equipped with a CPU (not illustrated), an I/O bus bridge 51 (a circuitry including multiple I/O bus bridge devices 52) for communicating with other boards, etc. The I/O board is a board equipped with an I/O device (not illustrated), the I/O bus bridges 51, and the like. The configuration controller board is a board having a capability to set, with respect to each I/O base bride 52 in each board, logical bus numbers of two buses connected with the I/O base bride 52 when the information system is activated, a capability to monitor the status (abnormality) of each boards, and so on.
This information system is a system that functions without troubles, if only the logical bus numbers are appropriately set to each I/O bus bridge 51 on each board. The configuration controller board in the existing information system has, nevertheless, only the capability to set logical bus numbers to all of the I/O bus bridge devices 52 in the system.
Therefore, when an I/O board of the existing information system fails, a reset of the information system is required to use a backup I/O board in place of the failed I/O board even if the backup I/O board already exists in the system. A reset is also required to add an I/O board to the existing information system.