Checkpoint-free in log mining for distributed information sharing

• US 9,009,104 B2
• Filed: 08/10/2010
• Issued: 04/14/2015
• Est. Priority Date: 07/31/2007
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Wong, Lik, Arora, Nimar S., Schmidt, Cristina, Gao, Lei, Hoang, Thuyan
• Primary Examiner(s): Fan, Shiow-Jy
• Application Number:
  US12/853,991
• Publication Number:
  US 20110010392A1
• Time in Patent Office: 1,708 Days
• Field of Search: 707/610, 707/E17.014, 707/999.2, 707/776
• US Class Current: 707/610
• CPC Class Codes: G06F 16/2358 Change logging, detection, and notification replication G06F16/27

Abstract

Techniques for replicating data between database systems without taking checkpoints are provided. In an embodiment, a capture process restarts. Upon restarting, the capture process reestablishes an association with an apply process. A particular logical time maintained by the apply process is then communicated to the capture process. Upon receiving the particular logical time, the capture process restarts mining from this particular logical time.

Claims

1. A method comprising:

on a source node, a capture process mining one or more transaction logs to generate logical change records at said source node;

said capture process transmitting said logical change records to an apply process running on a destination node for said apply process to apply the logical change records at said destination node;

wherein each logical change record of said logical change records is associated with a source logical time;

wherein said apply process of said destination node maintains a particular source logical time representing a bounded safe time point in the one or more transaction logs to begin mining on said source node with respect to said apply process, wherein said particular source logical time is based on logical change records received by said apply process at said destination node;

on said source node, a restarted capture process reestablishing an association with said apply process of said destination node;

said source node receiving, from said destination node, the particular source logical time;

in a checkpoint-free mode, said restarted capture process restarting mining of the one or more transaction logs based on said particular source logical time received from said destination node;

wherein said restarting mining in the checkpoint-free mode does not require checkpoints taken by the capture process;

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

2. The method of claim 1, further comprising said source node assigning system change numbers to source node transactions that are associated with said logical change records at said source node, and wherein said particular source logical time is one of said system change numbers.

3. The method of claim 1, further comprising said source node assigning system change numbers to said logical change records at said source node, and wherein said particular source logical time is one of said system change numbers.

4. The method of claim 1, wherein said capture process does not save any checkpoint information and wherein said restarted capture process does not retrieve any checkpoint information.

5. The A method of claim 1, further comprising said capture process preventing logical change records of inflight transactions at said source node at said logical time of said source node from being sent to said apply process.

6. The method of claim 1, wherein the particular source logical time comprises a source logical time associated with a last logical change record, of said logical change records, applied by said apply process at said destination node.

7. The method of claim 1, wherein said apply process maintains said particular source logical time by persisting said particular source logical time.

8. The method of claim 7, wherein said source node receives said particular source logical time from said destination node by accessing said particular source logical time persisted by said apply process.

9. The method of claim 1, wherein said capture process skips one or more records of said one or more transaction logs.

10. The method of claim 1, wherein the particular source logical time comprises a source logical time associated with an earliest start transaction record for a transaction, of said logical change records, received by said apply process at said destination node, wherein the transaction is not yet applied.

11. A non-transitory machine-readable storage medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform:

on a source node, a capture process mining one or more transaction logs to generate logical change records at said source node;

said capture process transmitting said logical change records to an apply process running on a destination node for said apply process to apply the logical change records at said destination node;

wherein each logical change record of said logical change records is associated with a source logical time;

wherein said apply process of said destination node maintains a particular source logical time representing a bounded safe time point in the one or more transaction logs to begin mining on said source node with respect to said apply process, wherein said particular source logical time is based on logical change records received by said apply process at said destination node;

on said source node, a restarted capture process reestablishing an association with said apply process of said destination node;

said source node receiving, from said destination node, the particular source logical time;

in a checkpoint-free mode, said restarted capture process restarting mining of the one or more transaction logs based on said particular source logical time received from said destination node

wherein said restarting mining in the checkpoint-free mode does not require checkpoints taken by the capture process.

12. The non-transitory machine-readable storage medium of claim 11, the one or more sequences of instructions which, when executed by the one or more processors, further causes said source node assigning system change numbers to source node transactions that are associated with said logical change records at said source node, and wherein said particular source logical time is one of said system change numbers.

13. The non-transitory machine-readable storage medium of claim 11, the one or more sequences of instructions which, when executed by the one or more processors, further causes said source node assigning system change numbers to said logical change records at said source node, and wherein said particular source logical time is one of said system change numbers.

14. The non-transitory machine-readable storage medium of claim 11, wherein said capture process does not save any checkpoint information and wherein said restarted capture process does not retrieve any checkpoint information.

15. The non-transitory machine-readable storage medium of claim 11, the one or more sequences of instructions which, when executed by the one or more processors, further causes said capture process preventing logical change records of inflight transactions at said source node at said logical time of said source node from being sent to said apply process.

16. The non-transitory machine-readable storage medium of claim 11, wherein the particular source logical time comprises a source logical time associated with a last logical change record, of said logical change records, applied by said apply process at said destination node.

17. The non-transitory machine-readable storage medium of claim 11, wherein said apply process maintains said particular source logical time by persisting the particular source logical time.

18. The non-transitory machine-readable storage medium of claim 17, wherein said source node receives said particular source logical time from said destination node by accessing the particular source logical time persisted by said apply process.

19. The non-transitory machine-readable storage medium of claim 11, wherein said capture process skips one or more records of the one or more transaction logs.

20. The non-transitory machine-readable storage medium of claim 11, wherein the particular source logical time comprises a source logical time associated with an earliest start transaction record for a transaction, of said logical change records, received by said apply process at said destination node, wherein the transaction is not yet applied.