Apparatus and method for validating a database record before applying journal data

• US 20030217031A1
• Filed: 05/16/2002
• Published: 11/20/2003
• Est. Priority Date: 05/16/2002
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Youngren, Larry William, Ricard, Gary Ross, Owen, David Finian
• Granted Patent: US 6,968,349 B2
• Time in Patent Office: Days
• US Class Current: 707/1
• CPC Class Codes: G06F 11/1004 to protect a block of data words, e.g. CRC or checksum G06F11/1076 takes precedence; security arrangements for protecting computers or computer systems against unauthorized activity G06F21/00
• CPC Class Codes: G06F 16/2358 Change logging, detection, and notification replication G06F16/27
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

An apparatus and method includes a database journal that records journal entries. Each journal entry includes a validation value that is computed from the data and metadata for the record before it is changed. In this manner, journal entries may be applied with confidence to a record in a database. This is especially useful when minimized data journal entries are used. If the validation value of the journal entry matches the validation value computed from the data and metadata of the record that the journal entry is to be applied to, then the record before applying the journal entry is identical to the record in the original database, and the journal data may be applied to the database record. If the validation value of the journal entry does not match the validation value computed from the data and metadata of the record that the journal entry is to be applied to, the record is not the same as in the original database when the journal entry was generated. As a result, an error message is generated to indicate that an error was encountered when applying the journal entry. In this manner, the apparatus and method of the preferred embodiments automatically validate a database record before applying journal data to the record.

Claims

1. An apparatus comprising:

(A) at least one processor;

(B) a memory coupled to the at least one processor;

(C) a database journal residing in the memory, the database journal including a journal entry for a selected record in a database, wherein the journal entry includes;

(C1) an indication of a change to at least one portion of the selected record; and

(C2) a validation value that represents a state of the selected record in the database before making the change to the selected record.

2. The apparatus of claim 1 wherein the indication of change lists less than all data in the selected record.

3. The apparatus of claim 1 wherein the validation value comprises a checksum.

4. The apparatus of claim 1 wherein the validation value is computed from data in the selected record.

5. The apparatus of claim 4 wherein the validation value is further computed from metadata for the selected record.

6. The apparatus of claim 1 wherein the validation value is substantially unique for data values stored in the selected record.

7. An apparatus comprising:

(A) at least one processor;

(B) a memory coupled to the at least one processor;

(C) a database residing in the memory; and

(D) a database journal residing in the memory, wherein the database journal includes a journal entry for a selected record in a database, wherein the journal entry includes;

(D1) an indication of a change to at least one portion of the selected record; and

(D2) a checksum that represents a state of the selected record in the database before making the change to the at least one portion, the checksum being computed from data in the selected record before making the change and from metadata for the selected record.

8. A method for journaling changes in a database comprising the steps of:

(1) determining when a change to a selected record in the database needs to be made;

(2) before making the change to the selected record, computing a validation value that represents a state of the selected record in the database; and

(3) storing the validation value in a journal entry that indicates the change to the selected record.

9. The method of claim 8 further comprising the step of making the change to the selected record.

10. The method of claim 8 wherein the journal entry includes an indication of change that lists less than all data in the selected record.

11. The method of claim 8 wherein the validation value comprises a checksum.

12. The method of claim 8 wherein step (2) computes the validation value from data in the selected record.

13. The method of claim 12 wherein step (2) further computes the validation value from metadata for the selected record.

14. The method of claim 8 wherein the validation value is substantially unique for data values stored in the selected record.

15. A method for replicating a first database in a source location to a second database in a target location, the method comprising the steps of:

(1) at the source location, performing the steps of;

(1A) determining when a change to a selected record in the first database needs to be made;

(1B) before making the change to the selected record, generating a journal entry for the selected record that includes;

(1B1) an indication of a change to at least one portion of the selected record; and

(1B2) a validation value that represents a state of the selected record in the first database before making the change to the at least one portion;

(2) transmitting the journal entry to the target location;

(3) at the target location, performing the steps of;

(3A) computing a validation value for a record in the second database that corresponds to the selected record in the first database;

(3B) comparing the validation value for the corresponding record in the second database to the validation value in the transmitted journal entry; and

(3C) if the validation values in step (3B) match, applying the transmitted journal entry to the second database.

16. The method of claim 15 further comprising the step of:

(3D) if the validation values in step (3B) do not match, providing an error message.

17. The method of claim 15 wherein the journal entry includes an indication of change that lists less than all data in the selected record.

18. The method of claim 15 wherein the validation value comprises a checksum.

19. The method of claim 15 wherein step (2) computes the validation value from data in the selected record.

20. The method of claim 19 wherein step (2) further computes the validation value from metadata for the selected record.

21. The method of claim 15 wherein the validation value is substantially unique for data values stored in the selected record.

22. A method for applying a journal entry to a corresponding record in a database, the method comprising the steps of:

(1) reading a validation value stored in the journal entry, wherein the validation value represents a state of the corresponding record in the database before making the change to at least one portion of the record;

(2) computing a validation value for the corresponding record in the database;

(3) comparing the validation value for the corresponding record in the database to the validation value stored in the journal entry; and

(4) if the validation values in step (3) match, applying the journal entry to the database.

23. The method of claim 22 further comprising the step of:

(5) if the validation values in step (3) do not match, providing an error message.

24. The method of claim 22 wherein the validation value comprises a checksum.

25. The method of claim 22 wherein the validation value is computed from data in the selected record.

26. The method of claim 25 wherein the validation value is further computed from metadata for the selected record.

27. A program product comprising:

(A) a database journal that includes a journal entry for a selected record in a database, wherein the journal entry includes;

(A1) an indication of a change to at least one portion of the selected record; and

(A2) a validation value that represents a state of the selected record in the database before making the change to the selected record.; and

(B) computer-readable signal bearing media bearing the database journal.

28. The program product of claim 27 wherein the computer-readable signal bearing media comprises recordable media.

29. The program product of claim 27 wherein the computer-readable signal bearing media comprises transmission media.

30. The program product of claim 27 further comprising a database journaling mechanism on the computer-readable signal bearing media for generating the database journal.

31. The program product of claim 27 wherein the indication of change lists less than all data in the selected record.

32. The program product of claim 27 wherein the validation value comprises a checksum.

33. The program product of claim 27 wherein the validation value is computed from data in the selected record.

34. The program product of claim 33 wherein the validation value is further computed from metadata for the selected record.

35. The program product of claim 27 wherein the validation value is substantially unique for data values stored in the selected record.

36. A program product comprising:

(A) a database journal that includes a journal entry for a selected record in a database, wherein the journal entry includes;

(A1) an indication of a change to at least one portion of the selected record; and

(A2) a checksum that represents a state of the selected record in the database before making the change to the at least one portion, the checksum being computed from data in the selected record before making the change and from metadata for the selected record; and

(B) computer-readable signal bearing media bearing the database journal.

37. The program product of claim 36 wherein the computer-readable signal bearing media comprises recordable media.

38. The program product of claim 36 wherein the computer-readable signal bearing media comprises transmission media.