Preventing change cycling using rules and redo tags in a redo log

• US 7,565,379 B2
• Filed: 05/30/2003
• Issued: 07/21/2009
• Est. Priority Date: 08/01/2002
• Status: Active Grant

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle International Corporation (Oracle Corporation)
• Inventors: Wang, Wei, Wong, Lik, Stamos, James, Lu, Edwina, Kaluskar, Sanjay, Bhatt, Neerja
• Primary Examiner(s): Wong; Don
• Assistant Examiner(s): DANG, THANH HA T
• Application Number:
  US10/452,761
• Publication Number:
  US 20040034619A1
• Time in Patent Office: 2,244 Days
• Field of Search: 707/200, 707/10, 707/100, 707/104.1
• US Class Current: 1/1
• CPC Class Codes: G06F 11/2097 maintaining the standby controller/processing unit updated initialisation or re-synchronisation thereof G06F11/1658 and subgroups
• 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 7/00 Methods or arrangements for processing data by operating upon the order or content of the data handled logic circuits H03K19/00
• CPC Class Codes: Y10S 707/99945 Object-oriented database structure processing

Abstract

In some messaging system architectures, messages can cycle back to the originator of a message, who may then propagate the message, causing the cycle to be repeated. Described herein are techniques that use rules and fields in a redo log, to manage message flows such that undesired cycles are prevented. The techniques may be used in messaging systems that have various topologies.

Claims

1. A method used for replicating particular changes to data made at a source database, the method comprising the steps of:

an apply process applying to data at a destination database server a message describing a particular change of said particular changes;

wherein the step of applying causes generating a first redo record in a redo log, wherein the redo log contains redo records that record changes made to data at said destination database server, wherein said redo records include said first redo record, wherein said first redo record records a first change made by said apply process to data at said destination database server;

wherein said particular change comprises either;

a data definition change to a database object of said source database, or a data manipulation change to a database object of said source database;

wherein said first redo record includes a first value in a first field that specifies that said first change was caused by said process applying messages, said first value not identifying any particular database server;

a capture process scanning said redo log for redo records, including said first redo record, for which to generate messages for said changes made to said data at said destination database server; and

said capture process foregoing generating a message for said first redo record in response to detecting that said first field in said first redo record holds said first value.

2. The method of claim 1, wherein:

said capture process requests an evaluation of a set of rules by a rules engine; and

wherein said capture process foregoes generating said message based on the evaluation of said set of rules.

3. The method of claim 2, wherein said set of rules contains at least one rule with at least one condition based on said first field.

4. The method of claim 3, wherein said at least one rule is associated with an evaluation context that includes attributes that are referenced by said at least one rule, said attributes including at least one attribute that reflects said first value.

5. The method of claim 3, wherein:

said apply process is associated with a session on said destination database server; and

said first field is set by said destination database server in response to detecting that the attribute associated with said session is set to a particular value.

6. The method of claim 2, further including the steps of:

before all values of a set of values that are needed to evaluate all rules in said set of rules are available, making a determination of whether said set of rules necessarily evaluates to a particular result;

wherein said set of values include a particular value based on said first value; and

wherein said determination is based on said particular value.

7. The method of claim 6, the method further including the steps of:

storing in a cache a result value that indicates a result of evaluating the set of rules based on a subset of values that includes less than all values of the set of values;

wherein the subset of values includes the particular value;

wherein said result value is stored in association with the subset of values.

8. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 1.

9. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 2.

10. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 3.

11. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 4.

12. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 5.

13. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 6.

14. A computer-readable storage medium storing one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 7.