Method and system for managing multiple database storage units

• US 6,801,921 B2
• Filed: 07/17/2001
• Issued: 10/05/2004
• Est. Priority Date: 09/08/2000
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yamashita, Nobuyuki, Kawamura, Nobuo, Tsuchida, Masashi
• Primary Examiner(s): Alam, Shahid
• Assistant Examiner(s): Ehichioya, Fred
• Application Number:
  US09/907,049
• Publication Number:
  US 20020107878A1
• Time in Patent Office: 1,176 Days
• Field of Search: 707/4, 707/8, 707/10, 707/100, 707/201, 707/202, 707/1, 707/2, 707/103.R, 707/104.1, 707/200, 707/204, 707/205, 711/122, 711/162, 711/112, 711/114, 711/154, 370/299, 370/369, 370/372, 370/389.4, 370/395.4, 370/477, 370/503, 370/539, 705/21, 705/30, 709/202, 709/203, 709/204, 709/208, 709/211, 709/219, 709/221, 709/223, 709/231, 709/232, 709/234, 709/318, 709/328
• US Class Current: 1/1
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence
• CPC Class Codes: G06F 11/2097 maintaining the standby controller/processing unit updated initialisation or re-synchronisation thereof G06F11/1658 and subgroups
• CPC Class Codes: G06F 16/27 Replication, distribution or synchronisation of data between databases or within a distributed database system; Distributed database system architectures therefor
• CPC Class Codes: G06F 2201/80 Database-specific techniques
• CPC Class Codes: Y10S 707/954 Relational
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99932 Access augmentation or optimizing
• CPC Class Codes: Y10S 707/99934 Query formulation, input preparation, or translation
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99945 Object-oriented database structure processing
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

The system manages at least a database in multiple database storage units, and the database is duplicated for redundancy. The system maintains the database redundancy for security. The system enables the maintenance and reorganization of the database storage units without interrupting the on-going operations involving the access to the database storage units. The non-stop ongoing database access is available by allocating a pair of a main storage unit and an intermediate storage unit that maintains the substantially identical data. During certain predetermined operations, the main storage unit is being dedicating to the on-going transactions while the intermediate database storage unit is manipulated to contain data that corresponds to a specified time. For example, the content of the intermediate storage is subsequently copied or used to update another database. When the above duplication or incorporation is completed, the intermediate storage unit is updated for the transactions that have taken place during the above operations to be synchronized with the main storage unit.

Claims

1. A method of managing a plurality of databases in response to continuous transactions, the databases including at least a first database, a second database and a third database, comprising:

simultaneously maintaining first data in the first database and a duplicate set of second data in the second database in response to database transactions;

determining a point in time for a predetermined database management task;

discontinuing the database transactions to and from the second database;

continuing the database transactions to and from the first database;

rolling back the second data in the second database to the point in time;

connecting the second database to the third database;

extracting a portion of the rolled back second data;

updating the third data in the third database based upon the extracted from the second database;

rolling forward the second data in the second database to match the first data in the first database; and

resuming the database transactions to and from the second database.

2. The method of managing a plurality of databases according to claim 1 further comprising updating a system log for keeping records for changes in the first database.

3. The method of managing a plurality of databases according to claim 2 wherein said rolling back of the second data in the second database is accomplished based upon the system log.

4. The method of managing a plurality of databases according to claim 2 wherein said rolling forward of the second data in the second database is accomplished based upon the system log.

5. The method of managing a plurality of databases according to claim 1 wherein the first database and the second database are maintained by a disk hardware unit.

6. The method of managing a plurality of databases according to claim 1 wherein the first database and the second database are maintained by a software program.

7. The method of managing a plurality of databases according to claim 1 wherein said resolving the second database and the third database is accomplished by connecting the second database to the third database and by incorporating the second data from the second database into the third database.

8. The method of managing a plurality of databases according to claim 7 wherein said incorporating the second data is accomplished for balancing a load among storage areas within the third database.

9. The method of managing a plurality of databases according to claim 8 wherein said balancing is accomplished by a predetermined sort algorithm.

10. The method of managing a plurality of databases according to claim 1 further comprising updating a differential log for keeping records for changes in the first database.

11. A system for managing a plurality of databases in response to continuous transactions, the databases including at least a first database, a second database and a third database, comprising:

a first database storage unit for storing first data in first database;

a second database storage unit for storing a duplicate set of second data in second database;

a third database storage unit for storing a duplicate set of third data in third database; and

a database management unit connected to said first database storage unit, said second database storage unit and said third database storage unit for continuing database transactions to and from the first database as well as simultaneously maintaining the first data in the first database and the duplicate set of the second data in the second database, said database management unit determining a point in time for a predetermined database management task and discontinuing the database transactions to and from the second database so as to roll back the second data in the second database to said point in time, said database management unit connecting the second database to the third database and updating the third data in the third database based upon the rolled back second data in the second database, said database management unit further comprising a database extraction unit connected to said second database storage unit for extracting a portion of the second data from the second database and a database incorporating unit connected to said database extraction unit and said third database storage unit for incorporating the portion of the second data to the third data in the third database, said database management unit rolling forward the second data in the second database to match the first data in the first database so as to resume the database transactions to and from the second database in said second database storage unit.

12. The system for managing a plurality of databases according to claim 11 further comprises a system log unit connected to said database management unit for updating a system log for keeping records for changes in the first database.

13. The system for managing a plurality of databases according to claim 12 wherein said database management unit rolls back the second data in the second database based upon said system log.

14. The system for managing a plurality of databases according to claim 12 wherein said database management unit rolls forward the second data in the second database based upon said system log.

15. The system for managing a plurality of databases according to claim 11 further comprising a differential information unit connected to said first database storage unit for automatically updating the second database according to a disk write operation to the first database.

16. The system for managing a plurality of databases according to claim 11 wherein said database incorporating unit balances a load among storage areas within said third database storage unit.

17. The system for managing a plurality of databases according to claim 16 wherein said database incorporating unit balances according to a predetermined sort algorithm.