Data search method wherein the court-key-data (ckd) storage subsystem

Abstract

For a computer system having a central processing unit, an external storage unit which records data in a count-key-data (CKD) format, and a storage control unit with a cache memory for controlling data transfer between the external storage unit and the central processing unit, a computer system and data search method is provided which can prevent the performance of the central processing unit from being lowered and can eliminate signal transfer between the central processing unit and storage control unit during most of a data search operation period, by disconnecting the storage control unit from the central processing unit. During the data search operation, upon reception of a search command for the first record, a quasi completion report is issued to disconnect the storage control unit from the central processing unit. The storage control unit executes the search operation by using data loaded in the cache memory of the storage control unit. After data is searched, a search completion report is issued. Since the storage control unit is disconnected from the central processing unit during most of the data search operation period, the central processing unit is not occupied during this period by the storage control unit. Signal transfer is therefore unnecessary between the central processing unit and storage control unit during the data search operation period, making it possible to elongate a physical distance between the central processing unit and storage control unit.