PURPOSE: To perform the acquisition of optimum backup data where the whole backup and a difference backup are combined and to efficiently execute the receovery processing after the acquisition in short time.
CONSTITUTION: A backup processing means 36 detects the number of the present update data from the update bit map of a backup object medium 52, performs the whole backup if the number is larger than a reference value and performs a difference backup if the number is smaller than the reference value. After a backup acquisition, a merge means 38 reduces the number of medium by performing a copy coupling. A recovery processing means 40 performs the elimination of unnecessary media in a used medium and the restoration processing to a recovery medium 52 by the successive reading or the parallel reading of a backup destination medium 62 in the shortest time.
KOYASU TORU
IGARASHI ISAO
