Method and system of database management for replica database

A data processing unit, wherein

• in a data management system in an external storage unit provided with multiple storage areas for storing data, a multiple write mechanism that allows multiple write of same data, a multiple write cancellation mechanism that separates multi-written areas at an arbitrary time to allow independent reading/writing as different control areas, and a physical copy mechanism that allows mutual copying of data stored in respective areas, the data processing unit comprises:
• data synchronizing means;
• and
• data synchronization canceling means,
• wherein the data synchronizing means includes:
• a first status which allows both references and updates of all transactions in an operation of input/output to/from the external storage unit through a data cache area in a main storage unit in response to a data access request from a transaction;
• a second status which allows references of all transactions and updates of a transaction in progress, and prohibits an update of a newly generated transaction;
• a third status which allows references of all transactions and updates of a transaction in progress, and holds an update of a newly generated transaction;
• a fourth status which allows references of all transactions, and allows updates of all transactions only in a cache;
• a fifth status which allows a reference and/or update of a transaction in progress, and prohibits a reference and/or update of a newly generated transaction;
• and
• a sixth status which allows a reference and/or update of a transaction in progress, and holds a reference and/or update of a newly generated transaction, and
• the data synchronizing means allows in the respective statuses,
• a first transition for changing from the first status to the second or third status;
• a second transition whereby upon completion of all transactions in progress in the second or third status, all unwritten data in the data cache at that point in time are written into the external storage unit at once, and the status is changed to the fourth or first status;
• a third transition for changing from the fourth status to the first status;
• a fourth transition for changing from the first status to the fifth or sixth status;
• and
• a fifth transition whereby upon completion of all transactions in progress in the fifth or sixth status, all data in the data cache at that point in time are erased from the data cache, and the status is changed to the first status.

A data processing unit, wherein

• in a database management system in an external storage unit provided with multiple storage areas for storing data, a multiple write mechanism that allows multiple write of same data, a multiple write cancellation mechanism that separates multi-written areas at an arbitrary time to allow independent reading/writing as different control areas, and a physical copy mechanism that allows mutual copying of data stored in respective areas, the data processing unit comprising:
• data directory information dynamic copying means capable of copying, based on data directory information registered in the database management system to access the storage area in which a database is stored, common information independent of an access path of the storage area such as a name of the database and structural information, rewriting only information of the access path to the storage area to information of access to another arbitrary storage area, and dynamically adding second data directory information with a new name storing a name of a first data directory information of a copy source;
• data directory information dynamic registering means capable of registering a newly created second data directory information in the database management system or another database management system;
• and
• access target allocating means for changing, when the name of the first data directory information is stored in a second data directory information, a database access request from an application program to be executed according to the first data directory information so that the database access request is executed according to the second data directory information.