Abstract: A system is provided for duplication of an update database in a computer using partial data extraction. A copying module creates a copy database, including a partial copy, of the update database. A journal selecting module selects data, related to parts of the copy database in which the copy has finished, from an update data journal of the update database that is made when the copy database is being copied by the copying module. A duplication module updates the contents of the copy database created by the copying module with the contents of the update data journal selected by the journal selecting module.

Abstract: A database system consisting of a network database and a relational database. When a modification is made to the network database, update log data about the modification is created by an update log creating portion. An updating portion searches an address table for the storage position of an address contained in the update log data according to this data. This address storage position is correlated to the relational database. Therefore, the updating portion can locate the position of a data item on the relational database according to the discovered address storage position. The updating portion updates this data item and reflects contents of updating of the network database in the relational database.