Hitachi, Ltd.

Hideyuki Takatani

Norifumi Nishikawa

Satoshi Wakayama

Hitoshi Tanaka

Takeo Maruyama

Hiroyuki Yanaka

In a distributed database system including a plurality of database systems each having a database, wherein a database possessed by one of the database systems serves as an original database, and databases of the remaining database systems are produced by replicating the original database, the presence or absence of update contention of the same data in two database systems is detected. When data susceptible to detection of update contention is updated, an update serial number is produced for the data. The update serial number includes a system identifier for identifying a database system in which the data is updated and an update frequency related to the number of times of updates. The update serial number is accumulatively stored in an update serial number history associated with the data each time the data is updated. When the updated data and the update serial number history associated therewith are transferred to a receiving database system, the contents of the update serial number history associated with the received data is compared with the contents of an update serial number history associated with data corresponding to the received data (target data) in a database of the receiving database system, and a contending state of the received data with the target data is determined based on the result of the comparison in the receiving database system.

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Omiya, Japan

Hideyuki Takatani