System and method for using a buffer to facilitate log catchup for online operations

• US 7,203,802 B2
• Filed: 04/29/2003
• Issued: 04/10/2007
• Est. Priority Date: 04/25/2003
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Huras, Matthew A., Winer, Michael J., McArthur, Catherine S., Hong, Quanhua, Zheng, Roger L. Q., Meadowcroft, Lorysa M., Thornborough, Shaun K.
• Primary Examiner(s): Elmore; Stephen C.
• Assistant Examiner(s): KIM, DANIEL Y
• Application Number:
  US10/425,163
• Publication Number:
  US 20040221030A1
• Time in Patent Office: 1,442 Days
• Field of Search: 709/224, 711/156, 711/154, 711/100, 711/102, 711/103, 711/104
• US Class Current: 711/154
• CPC Class Codes: G06F 16/2358 Change logging, detection, and notification replication G06F16/27

Abstract

A memory buffer facilitates log catchup for online operations. Certain designated areas of memory are allocated for one or more buffers for use during online operations (e.g., reorganization, create index, etc.). Concurrent update activities to the target object write informational records into the one or more buffers. If the buffers become full, the informational records may be written to logs for persistent storage. After online operations finish building all or a suitable portion of the shadow object, log catchup is performed by first applying activities in the informational records from the buffer and thereafter applying activities from logs, if necessary. The invention helps solve the drawbacks of log catchup since the buffer contains only the information related to the target shadow object. Also it does not involve physical I/Os, as these records are all in memory.

Claims

1. A processor-implemented information retrieval method for providing online operations in an application to replace a target object with a shadow object, wherein the application and the target object remain accessible to a plurality of users while the application is implementing the online operations, the method comprising:

in response to the online operations, dynamically allocating a buffer that is associated exclusively to the shadow object;

exclusively logging to the dynamically allocated buffer, the online activities of the target object, wherein the buffer is stored in a non-persistent memory having a faster response time than a persistent memory; and

applying the logged online activities from the dynamically allocated buffer to the shadow object to catchup the shadow object to the target object without using physical input/output operations (I/Os), thus enabling a faster response time compared to the use of the persistent memory.

2. The method of claim 1, further comprising, prior to exclusively logging to the dynamically allocated buffer, logging, to a log, the online activities of the target object, for storage to a persistent storage memory.

3. The method of claim 2, wherein applying the logged online activities from the dynamically allocated buffer to the shadow object comprises obtaining from the dynamically allocated buffer the activities logged to the dynamically allocated buffer, and obtaining from the log, the activities that have been logged exclusively to the log.

4. The method of claim 1, wherein the the dynamically allocated buffer includes a plurality of buffers, and wherein the log includes a plurality of logs.

5. The method of claim 4, wherein dynamically allocating the buffer includes sequentially allocating the buffers in response to the online activities.

6. The method of claim 4, further comprising reusing a used buffer from which online operations have been applied for the logging.

7. The method of claim 4, further comprising reusing a used buffer when available, before allocating the dynamically allocated buffer.

8. The method of claim 1, wherein the steps of exclusively logging to the dynamically allocated buffer and applying the logged online activities are performed concurrently.

9. The method of claim 1, further comprising selectively suspending the step of applying the logged online activities and resuming the step of applying the logged online activities to facilitate the online operations.

10. The method of claim 1, further comprising selectively suspending the online activities to the target object.

11. The method of claim 10, further comprising monitoring the step of applying the logged online activities relative to the step of exclusively logging to the dynamically allocated buffer, and performing the step of suspending the online activities in response to the step of monitoring.

12. The method of claim 2, wherein logging to the dynamically allocated buffer comprises flagging a successful logging to the log;

and

wherein applying the logged online activities comprises applying the online activities from the dynamically allocated buffer in response to the step of flagging.

13. A processor-implemented information retrieval system for providing online operations in an application to replace a target object with a shadow object, wherein the application and the target object remain accessible to a plurality of users while the application is implementing the online operations, the system comprising:

a writer for dynamically allocating a buffer that is associated exclusively to the shadow object, in response to the online operations;

a buffer logging mechanism for exclusively logging to the dynamically allocated buffer the online activities of the target object;

wherein the buffer is stored in a non-persistent memory having a faster response time than a persistent memory; and

an online operations provider for applying the logged online activities from the dynamically allocated buffer to the shadow object to catchup the shadow object to the target object without using physical input/output operations (I/Os), thus enabling a faster response time compared to the use of the persistent memory.

14. The system of claim 13, further comprising a persistent logging mechanism for logging to a log the online activities of the target object, the log for storage to a persistent storage memory, prior to exclusively logging to the dynamically allocated buffer.

15. The system of claim 14, wherein the online operations provider obtains from the dynamically allocated buffer the activities logged to the dynamically allocated buffer, and further obtains, from the log, activities that have been logged exclusively to the log.

16. The system of claim 13, wherein the dynamically allocated buffer includes a plurality of buffers, and wherein the log includes a plurality of logs.

17. The system of claim 16, wherein the buffer logging mechanism sequentially allocates the buffers in response to the online activities.

18. The system of claim 16, wherein the buffer logging mechanism reuses a used buffer from which online operations have been applied.

19. The system of claim 16, wherein the buffer logging mechanism reuses a used buffer when available before allocating the dynamically allocated buffer.

20. The system of claim 13, wherein the online operations provider applies the online activities from the dynamically allocated buffer concurrently, as the dynamically allocated buffer logging mechanism performs the logging.

21. The system of claim 13, wherein the online operations provider selectively suspends the logged online operations, and then resumes the logged online operations, to facilitate the online operations.

22. The system of claim 13, wherein the online operations provider suspends the online activities to the target object.

23. The system of claim 22, wherein the online operations provider monitors the applied logged online activities, and suspends the online activities in response to monitoring operations.

24. The system of claim 14, wherein the buffer logging mechanism flags a successful logging to the log;

and

wherein the online operations provider applies the online activities from the dynamically allocated buffer in response to a flagging operation.

25. A processor-implemented information retrieval system providing online operations that includes a computer program product having executable instruction codes stored on a computer usable medium, for providing online operations in an application to replace a target object with a shadow object, wherein the application and the target object remain accessible to a plurality of users while the application is implementing the online operations, the computer program product comprising:

a set of instruction codes for dynamically allocating a buffer that is associated exclusively to the shadow object, in response to the online operations;

a set of instruction codes for exclusively logging to the dynamically allocated buffer, the online activities of the target object;

wherein the buffer is stored in a non-persistent memory having a faster response time than a persistent memory; and

a set of instruction codes for applying the logged online activities from the dynamically allocated buffer to the shadow object to catchup the shadow object to the target object without using physical input/output operations (I/Os), thus enabling a faster response time compared to the use of the persistent memory.

26. The computer program product of claim 25, further comprising a set of instruction codes for logging, to a log, the online activities of the target object, for storage to a persistent storage memory, prior to exclusively logging to the dynamically allocated buffer.

27. The computer program product of claim 26, wherein the set of instruction codes for applying the logged online activities from the dynamically allocated buffer to the shadow object obtains, from the dynamically allocated buffer, the activities that have been logged to the dynamically allocated buffer, and further obtains from the log, the activities that have been exclusively logged to the log.

28. The computer program product of claim 25, wherein the the dynamically allocated buffer includes a plurality of buffers, and wherein the log includes a plurality of logs.

29. The computer program product of claim 28, wherein the set of instruction codes for dynamically allocating the buffer sequentially allocates the buffers in response to the online activities.

30. The computer program product of claim 28, further comprising a set of instruction codes for reusing a used buffer from which online operations have been applied.

31. The computer program product of claim 28, further comprising a set of instruction codes for reusing a used buffer when available, before allocating a buffer.