Hitachi, Ltd.

Hitachi Computer Peripherals Co., Ltd.

Toshiaki Hatanaka

Hidetoshi Sakaki

Katsunori Nakamura

Akira Kurano

Takehiro Ishikawa

Hiroshi Nishijima

Masami Maeda

Yukio Myoujin

Hiroshi Nishizima

A method, apparatus and computer program for controlling data migration in an information processing system which includes a central processing unit (CPU), a new storage system connected to the CPU and an old storage system connected to the new storage system. In the information processing system data migration is conducted to transfer data from the old storage system to the new storage system. The invention operates by permitting access by the CPU to the storage systems during data migration. When an access by the CPU is generated the invention determines whether the access is to a region where data migration has been completed or to a region where data migration has not been completed. If the access is to a region where data migration has been completed, then processing of the access is handled by the new storage system. If the access is to a region where data migration has not been completed, then processing of the access is handled by the old storage system causing data related to the access to be transferred from the old storage system to the new storage system. The speed of data migration can be adjusted based upon the utilization of the resources of the information processing system and information of the priority of access to the new storage system by the CPU.

Method of data migration

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.

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

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Odawara, Japan

Toshiaki Hatanaka