This invention provides a control method of a remote copy system for establishing a disaster recovery system for transmitting data in database by a copy function between storage devices possessed by the storage device so as to minimize a public line necessary for the data transmission. In a remote copy system for transmitting data in a main storage device to a remote storage device, the main storage device classifies a group of logical volumes for ensuring the data update order into a plurality of small groups and sets the utilization of a side file at which the data transmission is interrupted. When the quantity of data collected in the side file exceeds a threshold, data transmission is interrupted in the order from a small group having a lower utilization of the side file without stopping the data transmission of all logical volumes in the group.