CONTROL METHOD FOR DISK CACHE

PURPOSE: To improve the availability of a disk cache in view of storage capacity by making many empty areas of the disk cache in a short time. CONSTITUTION: Entries 403 of cell numbers 5a to 51... corresponding to data 5a to 51... on a disk cache 5 managed by SCBs(slot control block) 4a to 4e set in a directory 4 managing the disk cache 5 are held in these SCBs in 1:1 correspondence to numbers of data; and when data is written in a disk device from the disk cache 5, occupancy capacities of data on the disk cache 5 which are managed by individual SCBs 4a to 4e are acquired by entry numbers of cell numbers of SCBs 4a to 4e, and data 5a to 51... managed by one of SCBs 4a to 4e which has the largest occupancy capacity are written in the disk device from the disk cache 5 to make an empty area in the disk cache 5.