System and method for decoupling object identification for the purpose of object switching in database systems

• US 7,099,889 B2
• Filed: 04/29/2003
• Issued: 08/29/2006
• Est. Priority Date: 03/14/2003
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Lau, Leo Tat Man, Huras, Matthew Albert, Sachedina, Aamer, Romanufa, Keriley K., Flasza, Miroslaw Adam, Winer, Michael Jeffrey, Berks, Robert T.
• Primary Examiner(s): Alam, Shahid
• Assistant Examiner(s): Ebirim, Emeka
• Application Number:
  US10/425,754
• Publication Number:
  US 20040220940A1
• Time in Patent Office: 1,218 Days
• Field of Search: 707 1- 10, 707/200, 707/201, 707/204, 707/101, 395/600, 709/201
• US Class Current: 707/695
• CPC Class Codes: G06F 16/20 of structured data, e.g. relational data
• CPC Class Codes: Y10S 707/955 Object-oriented
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99942 Manipulating data structure, e.g. compression, compaction, compilation
• CPC Class Codes: Y10S 707/99944 Object-oriented database structure
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

The use of a centralized version table allows for efficient object switching. Rather than synchronizing all database agents to recognize a newly created file as containing the most recent version of a given object, database agents requiring access to the given object need only consult the centralized version table to learn file identity information. That is, the database agents consult the centralized version table to determine which of the files associated with a given object contain the most recent version of the given object. Mechanisms associated with the use of the centralized version table also provide for efficient recovery from a failure that has occurred during an object switching transaction.

Claims

1. A processor-implemented management method for switching a database object in a database that stores a plurality of database objects, wherein multiple versions of database objects are stored in a plurality of files, each of the plurality of files being identified by a file handle, the method comprising:

creating a lookup version table that includes version tuples, wherein each version tuple comprises a file handle for a file and a version identification for the file, wherein the file handle and the version identification are decouplable, and wherein the version identification indicates a current version for the object represented by the file handle;

prior to a database object performing an operation against a selected database object, locating a version tuple in the lookup version table that corresponds to the selected database object;

upon locating the version tuple, locking the version tuple to prevent other database agents from performing an object switching transaction on the selected database object prior to performing the operation;

wherein decoupling the file handle from the version identification within the lookup version table eliminates explicit synchronization among all the database agents.

2. The method of claim 1, wherein upon performance of the operation, performing object switching and providing an updated version indication of a switched database object that corresponds to the selected database object.

3. The method of claim 2,

wherein upon completion of the object switching, permitting another database agent to perform another operation against the switched database object.

4. The method of claim 3, further comprising determining whether the version tuple exists in the centralized version table.

5. The method of claim 4,

wherein if it is determined that the version tuple does not vet exist, creating a new version tuple for the selected database object.

6. The method of claim 3, wherein locking the version tuple comprises

acquiring an exclusive lock on the version tuple.

7. The method of claim 5, further comprising releasing the exclusive lock on the version tuple so that new input and output operations against the selected database object is performed by the other database agents.

8. The method of claim 1, wherein the indication of the version is binary;

and

wherein providing the updated version indication of the switched database object comprises toggling the value of the indication of the version.

9. The method of claim 1, further comprising distinguishing between a file that stores a shadow version of the selected database object and a file that stores a current version of the selected database object.

10. The method of claim 9, further comprising updating the lookup version table to reflect which file stores the shadow version of the database object and which file stores the current version of the database object.

11. A management computer program product having instruction codes stored on a computer-useable medium for switching a database object in a database that stores a plurality of database objects, wherein multiple versions of database objects are stored in a plurality of files, each of the plurality of files being identified by a file handle, the computer program product comprising:

a program code for creating a lookup version table that includes version tuples, wherein each version tuple comprises a file handle for a file and a version identification for the file, wherein the file handle and the version identification are decouplable, and wherein the version identification indicatesa current version for the object represented by the file handle;

prior to a database object performing an operation against a selected database object, a program code locating a version tuple in the lookup version table that corresponds to the selected database object;

upon locating the version tuple, a program code locking the version tuple to prevent other database agents from performing an object switching transaction on the selected database object prior to performing the operation;

wherein decoupling the file handle from the version identification within the lookup version table eliminates explicit synchronization among all the database agents.

12. The computer program product of claim 11, wherein upon performance of the operation, a program code performing object switching and providing an updated version indication of a switched database object that corresponds to the selected database object.

13. The computer program product of claim 12,

wherein upon completion of the object switching, a program code permitting another database agent to perform another operation against the switched database object.

14. The computer program product of claim 13, further comprising a program code for determining whether the version tuple exists in the centralized version table.

15. The computer program product of claim 14,

wherein if the program code determines that the version tuple does not vet exist, the program code creates a new version tuple for the selected database object.

16. The computer program product of claim 13,

wherein the program code for locking the version tuple acquires an exclusive lock on the version tuple.

17. The computer program product of claim 15, further comprising a program code for releasing the exclusive lock on the version tuple so that new input and output operations against the selected database object is performed by the other database agents.

18. The computer program product of claim 11, wherein the indication of the version is binary;

and

wherein the program code for providing the updated version indication of the switched database object toggles the value of the indication of the version.

19. The computer program product of claim 11, further comprising a program code for distinguishing between a file that stores a shadow version of the selected database object and a file that stores a current version of the selected database object.

20. The computer program product of claim 19, further comprising a program code for updating the lookup version table to reflect which file stores the shadow version of the database object and which file stores the current version of the database object.

21. A processor-implemented management system for switching a database object in a database that stores a plurality of database objects, wherein multiple versions of database objects are stored in a plurality of files, each of the plurality of files being identified by a file handle, the system comprising:

a table manager for creating a lookup version table that includes version tuples, wherein each version tuple comprises a file handle for a file and a version identification for the file, wherein the file handle and the version identification are decouplable, and wherein the version identification indicates a current version for the object represented by the file handle;

prior to a database object performing an operation against a selected database object, the table manager locates a version tuple in the lookup version table that corresponds to the selected database object;

upon locating the version tuple, the table manager locks the version tuple to prevent other database agents from performing an object switching transaction on the selected database object prior to performing the operation;

wherein the table manager decouples the file handle from the version identification within the lookup version table to eliminate explicit synchronization among all the database agents.

22. The system of claim 21, wherein upon performance of the operation, a restore manager performs object switching and provides an updated version indication of a switched database object that corresponds to the selected database object.

23. The system of claim 22, wherein upon completion of the object switching, the table manager permits another database agent to perform another operation against the switched database object.

24. The system of claim 23, further comprising the table manager determining whether the version tuple exists in the centralized version table.

25. The system of claim 24, wherein if the table manager determines that the version tuple does not yet exist, the table manager creates a new version tuple for the selected database object.

26. The system of claim 23, wherein the table manager locks the version tuple by acquiring an exclusive lock on the version tuple.