Free spaces of a plurality of databases including the same data are monitored. The free spaces depend on fragmentation states of the respective databases. A first database is determined to be an active database, and a second database whose free space is larger than that of the first database is determined to be a standby database. Data relocation processing is performed on the second database, the data relocation processing including suspending data synchronization, initializing the standby database, copying data of the active database to the standby database, and resuming the data synchronization. Controlling is performed so that the data relocation processing is performed on a database other than the second database by changing the active database and the standby database.