Data synchronization with minimal table lock duration in asynchronous table replication

• US 10,185,632 B2
• Filed: 03/13/2015
• Issued: 01/22/2019
• Est. Priority Date: 11/25/2014
• Status: Active Grant

• Current Assignee: SAP SE
• Original Assignee: SAP SE
• Inventors: Lee, Juchang, Lee, Joo-Yeon, Kim, Kyu-Hwan, Kim, Deok-Hoe, Park, Kyungyul
• Primary Examiner(s): Burke, Jeff A
• Assistant Examiner(s): Vu, Thong H
• Application Number:
  US14/657,865
• Publication Number:
  US 20160147617A1
• Time in Patent Office: 1,411 Days
• Field of Search: 707612, 707613, 707769, 707625, 705 1, 705 30, 705 67
• CPC Class Codes: G06F 11/1464 for networked environments
• CPC Class Codes: G06F 11/1469 Backup restoration techniques
• 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 11/1662 the resynchronized component or unit being a persistent storage device re-synchronization of failed mirror storage G06F11/2082; rebuild or reconstruction of parity RAID storage G06F11/1008
• CPC Class Codes: G06F 11/2094 Redundant storage or storage space G06F11/2056 takes precedence
• 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
• CPC Class Codes: G06F 16/27 Replication, distribution or synchronisation of data between databases or within a distributed database system; Distributed database system architectures therefor
• CPC Class Codes: G06F 16/273 Asynchronous replication or reconciliation
• CPC Class Codes: G06F 16/955 using information identifiers, e.g. uniform resource locators [URL]
• CPC Class Codes: G06F 2201/80 Database-specific techniques
• CPC Class Codes: G06F 2201/835 Timestamp

Abstract

Disclosed herein are system, method, and computer program product embodiments for minimizing table lock duration during lost change resynchronization between a source table and a replica table. An embodiment operates by detecting a restart at a source node or a replica node. A source table at the source node is then locked based on the detection. A database transaction is then created for a lost change resynchronization operation and the source table is unlocked. The database transaction is then compared to another database transaction based on its timestamp. Based on the comparison, either the database transaction for the lost change resynchronization operation or the other database transaction is executed.

Claims

1. A computer implemented method for minimizing table lock duration during lost change resynchronization between a source table and a replica table, comprising:

detecting, by at least one processor, a restart at a source node or a replica node, the source node having a source table and the replica node having a replica table;

locking, by the at least one processor, the source table based on the detection;

creating, after the locking, by the at least one processor, a first database transaction performing a lost change resynchronization operation, wherein the lost change resynchronization operation is assigned a database transaction identifier and a timestamp representing the creation time of the first database transaction;

unlocking, after the creating, by the at least one processor, the source table;

comparing, by the at least one processor, the first database transaction to a second database transaction based on the timestamp of the first database transaction; and

selecting, by the at least one processor, for execution the first database transaction or the second database transaction based on the comparison;

wherein at least one of the detecting, locking, creating, unlocking, comparing, and selecting are performed by one or more computers.

2. The method of claim 1, wherein the restart at the source node or the replica node is caused by a respective crash of the source node or the replica node.

3. The method of claim 1, wherein locking the source table prevents the source table from being modified.

4. The method of claim 1, wherein the second database transaction has a timestamp representing the creation time of the second database transaction.

5. The method of claim 1, wherein the timestamp of the first database transaction has a different value from the timestamp of the second database transaction.

6. The method of claim 1, wherein the lost change resynchronization operation is based on comparing a row of the source table to an associated row of the replica table.

7. The method of claim 1, wherein the lost change resynchronization operation further comprises comparing a row-ID column of the row of the source table to a row-ID column of the associated row of the replica table.

21. The method of claim 1, wherein the lost change resynchronization operation comprises:

capturing write database transactions to the source table that are not synchronized to the replica table; and

replaying the captured write database transactions on the replica table in response to the restart at the source node or replica node.

22. The method of claim 1, wherein the lost change resynchronization operation is associated with a replication log entry.

23. The method of claim 21, wherein the second database transaction comprises an insert, update, or delete operation to the source table that is absent from the captured write database transactions.

24. The method of claim 1, wherein the lost change resynchronization operation applies one or more changes made to the source table to the replica table.

25. The method of claim 24, wherein the one or more changes made to the source table comprise write database transactions.

8. A system, comprising:

a memory; and

at least one processor coupled to the memory and configured to;

detect a restart at a source node or a replica node, the source node having a source table and the replica node having a replica table;

lock the source table based on the detection;

create, after the locking, a first database transaction performing a lost change resynchronization operation, wherein the lost change resynchronization operation is assigned a database transaction identifier and a timestamp representing the creation time of the first database transaction;

unlock, after the creating, the source table;

compare the first database transaction to a second database transaction based on the timestamp of the first database transaction; and

select for execution the first database transaction or the second database transaction based on the comparison.

9. The system of claim 8, wherein the restart at the source node or the replica node is caused by a respective crash of the source node or the replica node.

10. The system of claim 8, wherein locking the source table prevents the source table from being modified.

11. The system of claim 8, wherein the second database transaction has a timestamp representing the creation time of the second database transaction.

12. The system of claim 8, wherein the timestamp of the first database transaction has a different value from the timestamp of the second database transaction.

13. The system of claim 8, wherein the lost change resynchronization operation is based on comparing a row of the source table to an associated row of the replica table.

14. The system of claim 13, wherein the lost change resynchronization operation further comprises comparing a row-ID column of the row of the source table to a row-ID column of the associated row of the replica table.

15. A tangible computer-readable device having instructions stored thereon that, when executed by at least one computing device, causes the at least one computing device to perform operations comprising:

detecting a restart at a source node or a replica node, the source node having a source table and the replica node having a replica table;

locking the source table based on the detection;

creating, after the locking, a first database transaction performing a lost change resynchronization operation, wherein the lost change resynchronization operation is assigned a database transaction identifier and a timestamp representing the creation time of the first database transaction;

unlocking, after the creating, the source table;

comparing the first database transaction to a second database transaction based on the timestamp of the first database transaction; and

selecting for execution the first database transaction or the second database transaction based on the comparison.

16. The computer-readable device of claim 15, wherein the restart at the source node or the replica node is caused by a respective crash of the source node or the replica node.

17. The computer-readable device of claim 15, wherein locking the source table prevents the source table from being modified.

18. The computer-readable device of claim 15, wherein the second database transaction has a timestamp representing the creation time of the second database transaction.

19. The computer-readable device of claim 15, wherein the timestamp of the first database transaction has a different value from the timestamp of the second database transaction.

20. The computer-readable device of claim 15, wherein the lost change resynchronization operation is based on comparing a row of the source table to an associated row of the replica table.