Robust end-of-log processing

• US 20070136380A1
• Filed: 12/12/2005
• Published: 06/14/2007
• Est. Priority Date: 12/12/2005
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Cabrera, Luis, Kulesza, Jakub, Lindell, Steven, East, Jeffrey
• Granted Patent: US 7,756,838 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/1474 in transactions G06F16/20 takes precedence
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence
• CPC Class Codes: G06F 2201/82 Solving problems relating to consistency ensuring consistency in mirrored systems G06F11/2064

Abstract

A method of invalidating an unused log file in a database includes examining a discard log information storage area and determining if a discard log exists. If the discard log exists, the log is invalidated. The headers of each of the log files that have been fully invalidated are then invalidated. The discard log is then fully invalidated and a new log file may be generated on top of the discarded log. The method may be interrupted by a failure, a changeover, or crash and will be repeated until it completes.

Claims

1. A method of invalidating a transaction log file in a first database, the method comprising:

(a) reading discard log information from a storage area, the discard log information comprising an indicator that a discard log file exists, a starting point identifier of the discard log file, and an ending point identifier of the discard log file, the discard log file comprising at least one log block of transaction log that is to be discarded;

(b) writing an invalid data pattern into the at least one log block, wherein after writing, log block content is identifiable as invalid;

(c) resetting the discard log information, the reset clearing the indicator that the discard log file exists.

2. The method of claim 1, further comprising:

resuming the method from step (a) if a failover from the first database to a second database occurs in any of steps (a), (b), and (c).

3. The method of claim 1, further comprising invalidating header information of the at least one log block after step (b).

4. The method of claim 3, wherein writing an invalid data pattern into the at least one log block comprises writing the invalid data pattern into the at least one log block in a physical file order within a logical file beginning at a beginning logical sequence number and progressing to an end logical sequence number.

5. The method of claim 1, wherein writing an invalid data pattern into the at least one log block comprises writing an invalid data pattern into header information of log blocks that are invalidated.

6. The method of claim 5, wherein header information of a last log block is invalidated before header information of a preceding log block, wherein if a failover occurs, header information is retained in preceding log blocks to allow repeating the method.

7. The method of claim 1, wherein resetting the discard log information further comprises resetting the starting point identifier of the discard log file and the ending point identifier of the discard log file.

8. The method of claim 1, further comprising:

receiving new transaction log record information from a second database.

9. A method of invalidating a transaction log file in a first database, the method comprising:

(a) reading discard log information from a storage area, the discard log information comprising an indicator that a discard log file exists, a starting point identifier of the discard log file, and an ending point identifier of the discard log file, the discard log file comprising at least one log block of transaction log that is to be discarded;

(b) writing an invalid pattern of data into a first log block, wherein the first log block content is invalidated by an identifiable pattern of invalid data;

(c) updating the starting point identifier of the discard log file to correspond to a next log block following the first log block; and

(d) receiving new log file record information from a second database.

10. The method of claim 9, further comprising:

asynchronously invalidating a remaining portion of the discard log file.

11. The method of claim 10, wherein asynchronously invalidating a remaining portion of the discard log file comprises:

writing an identifiably invalid data pattern into log blocks of the discarded log file; and

writing an invalid data pattern into headers of the log blocks of the discarded log files.

12. The method of claim 10, further comprising:

resetting the discard log information, the reset clearing the indicator that the discard log file exists.

13. The method of claim 9, further comprising:

resuming the method from step (a) if a failover from the first database to a second database occurs in any of steps (a), (b), and (c).

14. The method of claim 9, wherein reading discard log information from a storage area further comprises reading a starting point identifier that is past the header of the at least one block.

15. The method of claim 9, wherein writing an invalid pattern of data into the at least one log block comprises writing an identifiably invalid data pattern into the at least one log block in a physical file order within a logical file beginning at a beginning logical sequence number and progressing to an end logical sequence number.

16. A computer-readable medium having computer-executable instructions for performing a method of invalidating a transaction log file in a first database, the method comprising:

(a) reading discard log information from a storage area, the discard log information comprising an indicator that a discard log file exists, a starting point identifier of the discard log file, and an ending point identifier of the discard log file, the discard log file comprising at least one log block of transaction log that is to be discarded;

(b) writing an identifiably invalid data pattern into the at least one log block, wherein log block content is rendered invalid;

(c) writing a pattern of identifiably invalid data into header information of the at least one log block; and

(d) resetting the discard log information, the reset clearing the indicator that the discard log file exists.

(e) resuming the method from step (a) if a failover from the first database to a second database occurs in any of steps (a), (b), (c), and (d).

17. The computer-readable medium of claim 16, wherein the step of method of writing an identifiably invalid data pattern into the at least one log block comprises writing an invalid data pattern into the at least one log block in a physical file order within a logical file beginning at a beginning logical sequence number and progressing to an end logical sequence number.

18. The computer-readable medium of claim 16, wherein the step of writing an identifiably invalid data pattern into the at least one log block comprises writing an invalid data pattern into header information of log blocks that are invalidated.

19. The computer-readable medium of claim 18, wherein header information of a last log block is invalidated before header information of a preceding log block, wherein if a failover occurs, header information is retained in preceding log blocks to allow repeating the method.

20. The computer-readable medium of claim 16, further comprising the step of:

receiving new transaction log record information from a second database.