When the redundant system operates the second node in place of the first node in the primary system and transmits, to the secondary system, data update information generated according to a data update in the second node, the fourth node the data update information generated according to the data update in the second node from the second node using the second inter-system transfer path. The fourth node changes by changing a direction of the second intra-system transfer, a configuration by which the data update information acquired by the fourth node is acquired by the third node using the second inter-system transfer path.