An apparatus for copying data to another apparatus including a receiving buffer, includes: a transmitting buffer including a plurality of areas for temporary storing data of the copying; and a processor for executing a process, including: receiving information indicative of an instantaneous vacant area of the receiving buffer of the another apparatus, the vacant area being capable of temporarily storing data that could be transmitted from the transmitting buffer, determining an area of the transmitting buffer that stores data to be transmitted subsequently in reference to the information of the vacant area, and transmitting data stored in the determined area of the transmitting buffer to the receiving buffer of the another apparatus.