Hitachi, Ltd.

Noriko Nagae

Nobuo Kawamura

Norihiro Hara

Takayoshi Shimokawa

This database system includes a first site that provides a database and a second site that stores a copy of said database. A first computer for the first site performs database processing and updates the data in the database. A first original storage for the first site transmits data to a second original storage for the second site asynchronously with respect to a database management unit, and a first duplicate storage for the first site transmits data to a second duplicate storage for the second site asynchronously with respect to the database management unit. A second computer for the second site compares the data in the second original storage with the data in the second duplicate with prescribed timing and restores the database if the data in the second original storage and the data in the second duplicate storage do not match.

Database system control method and database system

The data processing system controls, from the database management system on a host computer, the storage device subsystem which stores log data supplied from the database management system; allocates on a disk cache in the storage device subsystem in advance a log-dedicated buffer area of a size equal to that of the log data output between checkpoints; writes log data into the buffer area; and, in the event of a host computer failure, reads out the log data from the disk cache without making access to a disk device. Since the log information required for the recovery of the data processing device is cached on the storage device side, the time it takes to read the necessary log information can be shortened, which in turn reduces the system recovery time.

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Tokyo, Japan

Noriko Nagae