DUPLICATE DATA BASE ACCESS DEVICE AND ITS ACCESSING METHOD

摘要

PROBLEM TO BE SOLVED: To maintain consistency of a duplicate data base as continuing a transaction processing and to access a physical duplicate data base without changing an application program to access a data base at a duplicating origin when the physical duplicate data base is created by cutting off one of multiply written or duplicated data base areas on an external storage device. SOLUTION: When one of the multiply written or duplicated data base areas is cut off on the external storage device, a data base management system writes data at a state that the consistency is maintained in the external storage device and provides a means capable of controlling timing to cut off the duplicated data base areas. In addition, a new piece of physical definition information to be required for access to the duplicated data base is dynamically added based on the physical definition information of a data base at a duplicating origin and provides a means capable of selecting whether the data base on the duplicating origin is accessed or a data base at a duplicating destination is accessed is provided.