METHOD FOR MIRRORING A LOG FILE BY THRESHOLD DRIVEN SYNCHRONIZATION

• US 20120330897A1
• Filed: 06/29/2012
• Published: 12/27/2012
• Est. Priority Date: 03/11/2009
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Fashchik, Ran, Gordon, Eyal, Valentin, Gary
• Granted Patent: US 9,201,746 B2
• Time in Patent Office: Days
• US Class Current: 707/656
• CPC Class Codes: G06F 11/1471 involving logging of persistent data for recovery
• CPC Class Codes: G06F 11/2071 using a plurality of controllers
• CPC Class Codes: G06F 11/2074 Asynchronous techniques
• CPC Class Codes: G06F 11/2076 Synchronous techniques
• CPC Class Codes: G06F 16/2358 Change logging, detection, and notification replication G06F16/27

Abstract

A method for of accelerating database log hardening using specific per block data protection and damage control is provided. A per write specification is implemented to determine when database log data is mirrored synchronously or asynchronously. Synchronous mirroring is performed upon reaching a predetermined threshold, based on one or more parameters such as transaction value, both individual and cumulative, and the quantity of data written since the last synchronous mirroring. As data is added to the database log, it is written specifying asynchronous mirroring to the primary log file. Once a threshold is met, a write specifying synchronous mirroring is performed to both the primary and secondary log files, thereby hardening the log file in both primary and secondary storage subsystem.

Claims

1. A method of mirroring log data from a primary storage subsystem to a secondary storage subsystem, the method comprising:

initiating a transaction;

determining a value of the transaction;

adding the value of the transaction to a cumulative value of transaction values since a most recent synchronous mirroring;

performing an asynchronous mirroring of said log data when the cumulative value does not exceed a damage threshold; and

performing a synchronous mirroring of said log data when the cumulative value exceeds the damage threshold.

2. The method according to claim 1, wherein said log data is stored in a sequential database log file.

3. The method according to claim 1, wherein said transaction comprises one or more database transactions.

4. The method according to claim 1, wherein the value of the transaction is selected from a group consisting of a monetary value of the transaction and a quantity of data in the transaction.

5. The method according to claim 1, wherein the cumulative value is determined by incrementing a counter according to the value of the transaction.

6. The method according to claim 5, wherein incrementing said counter comprises:

receiving said log data; and

updating said counter with information derived from said received log data.

7. The method according to claim 5, wherein said counter is reset after performing the synchronous mirroring.

8. The method according to claim 1, wherein said performing the synchronous mirroring comprises updating said secondary storage system with log data received by the primary storage system after a most recent mirroring.

9. A computer program product for mirroring log data from a primary storage subsystem to a secondary storage subsystem, comprising:

a non-transitory computer usable medium having computer usable code embodied therewith, the computer program product comprising;

computer usable code configured for initiating a transaction;

computer usable code configured for determining a value of the transaction;

computer usable code configured for adding the value of the transaction to a cumulative value of transaction values since a most recent synchronous mirroring;

computer usable code configured for asynchronously mirroring of said log data when the cumulative value does not exceed a damage threshold;

computer usable code configured for synchronously mirroring said log data when the cumulative value exceeds the damage threshold.

10. The computer program product according to claim 9, wherein said log data is stored in a sequential database log file.

11. The computer program product according to claim 9, wherein said data comprises one or more database transactions.

12. The computer program product according to claim 9, wherein the value of the transaction is selected from a group consisting of a monetary value of the transaction and a quantity of data in the transaction.

13. The computer program product according to claim 9, wherein the cumulative value is determined by incrementing a counter according to the value of the transaction.

14. The computer program product according to claim 13, wherein incrementing said counter comprises:

computer usable code configured for receiving said log data; and

computer usable code configured for updating said one or more counters with information derived from said received log data.

15. The computer program product according to claim 9, wherein said computer usable code configured for synchronously mirroring updates said secondary storage system with log data received by the primary storage system after a most recent synchronous mirroring.

16. A method of mirroring database transaction log data from a primary storage subsystem to a secondary storage subsystem, the method comprising:

initializing a damage counter;

initiating several transactions;

upon initiating each transaction, determining a value of the transaction;

upon determining the value of each transaction, updating the damage counter based on the value of the transaction to a cumulative value of the transactions processed after a most recent synchronous mirroring; and

performing a synchronous mirroring of said log data when a value of said damage counter is greater than a damage threshold.

17. The method according to claim 16, wherein said database transaction log data is stored in a sequential file.

18. The method according to claim 16, wherein the value of the transaction is based on a quantity of the log data, wherein said updating the damage counter comprises:

receiving said transaction log data; and

updating said damage counter with the quantity of said received transaction log data.

19. The method according to claim 16, wherein said step of mirroring comprises the step of updating said secondary storage system with log data received after said most recent synchronous mirroring.

20. The method according to claim 16, further comprising reinitializing the damage counter.

21. A method of mirroring database transaction log data from a primary storage subsystem to a secondary storage subsystem, the method comprising:

initiating a transaction;

determining whether a physical data threshold is reached;

performing an asynchronous mirroring of said log data when the physical data threshold is not yet reached; and

performing a synchronous mirroring of said log data when said physical data threshold is reached.

22. The method according to claim 21, wherein said database transaction log data is stored in a sequential file.

23. The method according to claim 21, wherein said physical data threshold comprises one or more data tracks, each said track comprising a circular segment of a fixed disk comprising a consecutive set of sectors.

24. The method according to claim 23, wherein the one or more data tracks are copied during the synchronous mirroring.

25. The method according to claim 21, wherein said step of performing the synchronous mirroring comprises the step of updating said secondary storage system with log data received after said most recent synchronous mirroring.