Patent ID: 7917513

Claim:
A data processing system comprising: a processor device used for acquiring a group-of-clusters update information from a data control system, in response to an update check request, cluster update information which is computed by the data control system based on two or more pieces of the cluster update information stored in the data control system: a cache device for caching the cluster update information, wherein the cache unit comprises: a list of data elements to be duplicated, said data elements belonging to a single cluster of a plurality of clusters, wherein any same data element is made to belong to a same cluster; identifiers of the clusters to which the data elements belong; and the cluster update information received from the data control system, of which data value of the data elements to be duplicated has been updated, wherein said cluster update information is used as an update checksum indicating that the data element belonging to one of the plurality of clusters is updated; a group-of-clusters update information computation unit to compute group-of-clusters update information with respect to the group of clusters based on the two or more pieces of cluster update information having been cached, wherein said computation unit performs a hash function on the cluster update information for all of the clusters belonging to the group of clusters for every corresponding bit and then performs exclusive OR operations on results of the hash function; and wherein a cluster update information storage unit applies an initial value of cluster update information by using a predetermined hash function and the hash function which satisfies a collision difficulty in order to enhance accuracy in update detection; an update judging unit device to judge that the value obtained through the exclusive OR operation is a most recently updated group-of-clusters update information for the group of clusters, provided that the group-of-clusters update information coincides with the cluster update information acquired from the data control system, such that the data processing system is able to determine whether a cached data item is the most recently updated; and a data transmission device that transmits to the data control system group-of-clusters update information for updating the cluster update information for all of the clusters to which the cached data elements belong in the database such that the update information is duplicated across the data processing system, and such that the data control system does not need to perform a cache control on the data elements and clusters cached by the data processing system.