The present invention is constituted so as to enable the recovery of a database even when a log comprising a DB update history is not created. When executing a transaction in the logless mode, a logless-start log is created and written to a primary log VOL 55A at the start of this transaction, and this logless-start log is also written to a secondary log VOL 55B. Thereafter, batch processing is carried out for a DB of a primary DB VOL 51A, and while this transaction is being executed, the pair-split state of the DB VOL is cancelled either prior to the start or after the end of the batch processing, and if the difference between the DB VOLs is eliminated subsequent to the end of batch processing, a logless-end log is created and written to the primary log VOL 55A, and this log is also written to the secondary log VOL 55B.