Patent ID: 8051054

Claim:
A data update method to be executed by a database system in which a center apparatus and terminals each have a database management unit for managing each version by using logical structure data of a database as physical structure pages stored in a file of a disk device and running a same version, wherein: said center apparatus: responsive to an input of a center apparatus side-received command which said center apparatus receives as a representative of an update content common to said terminals, stores a result of applying said center apparatus side-received command to said logical structure data in a page of a DB area of the file, and creates an update difference file storing each difference page of each page in the DB area representative of a data change between a version before update and a version after update caused by said center apparatus side-received command; and said terminal: updates a page to said version after update after being applied with said center apparatus side-received command, by overwrite copying said difference page in said update difference file notified from said center apparatus to the page in a DB area of said terminal, responsive to a terminal side-received command representative of an update content to be applied to said terminal, stores a result of applying said terminal side-received command to said logical structure data in a page of a file in said DB area; stores a version before update of the page in said DB area whose version was changed from the version before update to a version after update by said terminal side-received command, in a backup file as a backup page; overwrites said backup page for the page subjected to a data change to said version after update by said terminal side-received command, prior to data update using said update difference file; in said process, responsive to an input of said terminal side-received command, of applying said terminal side-received command to said logical structure data, further records an input of said terminal side-received command in a sequential order in an update command history file; and after said process of overwriting the difference page to the page in the DB area of said terminal, further applies in a sequential order said terminal side-received command read from said update command history file to said logical structure data constituted of the pages of said version after update.