ELIMINATION OF LOG FILE SYNCHRONIZATION DELAY AT TRANSACTION COMMIT TIME

• US 20160350353A1
• Filed: 05/29/2015
• Published: 12/01/2016
• Est. Priority Date: 05/29/2015
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Li, Yunrui
• Granted Patent: US 10,599,630 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/2358 Change logging, detection, and notification replication G06F16/27
• CPC Class Codes: G06F 16/2365 Ensuring data consistency and integrity
• CPC Class Codes: G06F 16/2379 Updates performed during online database operations; commit processing

Abstract

A method and apparatus for elimination of log file synchronization delay at transaction commit time is provided. One or more change records corresponding to a database transaction are generated. One or more buffer entries comprising the one or more change records are entered into a persistent change log buffer. A commit operation is performed by generating a commit change record corresponding to the database transaction and entering a commit buffer entry comprising the commit change record into the persistent change log buffer. The commit operation returns without waiting for the commit change record to be recorded in a change record log file.

Claims

1. A method comprising:

generating one or more change records corresponding to a database transaction;

entering one or more buffer entries comprising the one or more change records into a persistent change log buffer;

performing a commit operation by;

generating a commit change record corresponding to the database transaction;

entering a commit buffer entry comprising the commit change record into the persistent change log buffer;

returning, by the commit operation, without waiting for the commit change record to be recorded in a change record log file;

wherein the method is performed by one or more computing devices.

2. The method of claim 1, wherein the persistent change log buffer is allocated in a non-volatile memory.

3. The method of claim 1, wherein the persistent change log buffer is allocated in a non-volatile memory of a computing node that is remote from a node executing a database instance that is executing the database transaction.

4. The method of claim 1, further comprising:

persistently storing a current write progress marker, wherein all buffer entries in the persistent change log buffer that are below the current write progress marker have been written to one or more change record log files.

5. The method of claim 4, further comprising:

determining an upper boundary based on a position of the current write progress marker within the persistent change log buffer and a size of the persistent change log buffer;

wherein no buffer entry is entered into the persistent change log buffer above the upper boundary.

6. The method of claim 5, further comprising, when the upper boundary indicates that no space is available in the persistent change log buffer, delaying entry of the one or more buffer entries until the current write process marker is moved forward.

7. The method of claim 1, further comprising:

performing a deferred write operation on one or more entered buffer entries in the persistent change log buffer, wherein the deferred write operation comprises writing one or more change records, corresponding to the one or more entered buffer entries, to the change record log file and clearing the one or more entered buffer entries from the persistent change log buffer;

wherein the deferred write operation is not synchronized with execution of commit operations.

8. The method of claim 1, further comprising:

performing a deferred write operation on one or more entered buffer entries in the persistent change log buffer, wherein the deferred write operation comprises writing, to a virtual change log file, change record metadata indicating one or more locations of the one or more entered change records within the persistent change log buffer;

wherein the deferred write operation is not synchronized with execution of commit operations.

9. The method of claim 1,

wherein the one or more change records are generated by a first process executing the database transaction;

wherein the first process is assigned a first address space within the persistent change log buffer;

wherein the one or more buffer entries and the commit buffer entry are entered in the first address space of the persistent change log buffer.

10. The method of claim 9, further comprising:

assigning a second address space within the persistent change log buffer to a second process executing a second transaction;

wherein the second process enters one or more second log buffer entries into the second address space of the persistent change log buffer;

wherein the first process uses the first address space and the second process uses the second address space concurrently without serialization between the first process and the second process.

11. The method of claim 1, further comprising:

detecting a failure of a database instance generating and entering change records into the persistent change log buffer;

scanning, by a recovery process, the persistent change log buffer to detect unwritten change records in the persistent change log buffer that were generated by the database instance;

writing the unwritten change records to the change record log file;

clearing the unwritten change records from the persistent change log buffer.

12. One or more non-transitory storage media storing instructions which, when executed by one or more computing devices, cause performance of:

generating one or more change records corresponding to a database transaction;

entering one or more buffer entries comprising the one or more change records into a persistent change log buffer;

performing a commit operation by;

generating a commit change record corresponding to the database transaction;

entering a commit buffer entry comprising the commit change record into the persistent change log buffer;

returning, by the commit operation, without waiting for the commit change record to be recorded in a change record log file.

13. The non-transitory storage media of claim 12, wherein the persistent change log buffer is allocated in a non-volatile memory.

14. The non-transitory storage media of claim 12, wherein the persistent change log buffer is allocated in a non-volatile memory of a computing node that is remote from a node executing a database instance that is executing the database transaction.

15. The non-transitory storage media of claim 12, wherein the instructions, when executed by the one or more computing devices, further cause performance of:

persistently storing a current write progress marker, wherein all buffer entries in the persistent change log buffer that are below the current write progress marker have been written to one or more change record log files.

16. The non-transitory storage media of claim 15, wherein the instructions, when executed by the one or more computing devices, further cause performance of:

determining an upper boundary based on a position of the current write progress marker within the persistent change log buffer and a size of the persistent change log buffer;

wherein no buffer entry is entered into the persistent change log buffer above the upper boundary.

17. The non-transitory storage media of claim 16, wherein the instructions, when executed by the one or more computing devices, further cause performance of:

when the upper boundary indicates that no space is available in the persistent change log buffer, delaying entry of the one or more buffer entries until the current write process marker is moved forward.

18. The non-transitory storage media of claim 12, wherein the instructions, when executed by the one or more computing devices, further cause performance of:

performing a deferred write operation on one or more entered buffer entries in the persistent change log buffer, wherein the deferred write operation comprises writing one or more change records, corresponding to the one or more entered buffer entries, to the change record log file and clearing the one or more entered buffer entries from the persistent change log buffer;

wherein the deferred write operation is not synchronized with execution of commit operations.

19. The non-transitory storage media of claim 12, wherein the instructions, when executed by the one or more computing devices, further cause performance of:

performing a deferred write operation on one or more entered buffer entries in the persistent change log buffer, wherein the deferred write operation comprises writing, to a virtual change log file, change record metadata indicating one or more locations of the one or more entered change records within the persistent change log buffer;

wherein the deferred write operation is not synchronized with execution of commit operations.

20. The non-transitory storage media of claim 12,

wherein generating the one or more change records comprises generating the one or more change records by a first process executing the database transaction;

wherein the instructions, when executed by the one or more computing devices, further cause performance of assigning the first process a first address space within the persistent change log buffer;

wherein entering the one or more buffer entries comprises entering the one or more buffer entries in the first address space of the persistent change log buffer;

wherein entering the commit buffer entry comprises entering the commit buffer entry in the first address space of the persistent change log buffer.

21. The non-transitory storage media of claim 20, wherein the instructions, when executed by the one or more computing devices, further cause performance of:

assigning a second address space within the persistent change log buffer to a second process executing a second transaction;

wherein the second process enters one or more second log buffer entries into the second address space of the persistent change log buffer;

wherein the first process uses the first address space and the second process uses the second address space concurrently without serialization between the first process and the second process.

22. The non-transitory storage media of claim 12, wherein the instructions, when executed by the one or more computing devices, further cause performance of:

detecting a failure of a database instance generating and entering change records into the persistent change log buffer;

scanning, by a recovery process, the persistent change log buffer to detect unwritten change records in the persistent change log buffer that are generated by the database instance;

writing the unwritten change records to the change record log file;

clearing the unwritten change records from the persistent change log buffer.