Method for data replication with conflict detection

• US 6,058,401 A
• Filed: 05/20/1998
• Issued: 05/02/2000
• Est. Priority Date: 03/19/1996
• Status: Expired due to Term

• Current Assignee: Oracle International Corporation (Oracle Corporation)
• Original Assignee: Oracle Corporation
• Inventors: Stamos, James, Doo, Lip Boon, Souder, Benny, Downing, Alan
• Primary Examiner(s): Homere, Jean R.
• Application Number:
  US09/081,297
• Time in Patent Office: 713 Days
• Field of Search: 701/201, 701/8, 701/102, 701/203, 701/2, 701/3, 701/10
• US Class Current: 1/1
• CPC Class Codes: G06F 11/2035 without idle spare hardware
• CPC Class Codes: G06F 11/2048 where the redundant components share neither address space nor persistent storage
• 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 16/2308 Concurrency control transaction processing G06F9/466
• CPC Class Codes: G06F 16/2315 Optimistic concurrency control
• CPC Class Codes: G06F 16/2322 using timestamps
• 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 2201/80 Database-specific techniques
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

Communication costs are reduced in a distributed system that supports data replication with conflict detection by sending small values or nulls as replacements for field values that are not strictly used for replication or conflict detection. Specifically, nulls are propagated for new values of unmodified fields, old values of fields in unmodified groups of linked fields, and old values of fields for which conflict detection has been disabled. Flag values that indicate which actual old and new values were sent may be generated and propagated along with the replicated data.

Claims

1. A method of maintaining multiple copies of a body of data organized into records of related fields, said method comprising the computer-implemented steps of:

determining whether a record within said body of data is updated at a first site;

in response to determining that the record was updated, propagating, to a second site, small values in place of at least one of actual old values and actual new values associated with said related fields of said updated record; and

determining whether a conflict exists within a corresponding record at said second site based on said propagated small values and said propagated actual old values; and

if said conflict does not exist, then updating said corresponding record based on at least said propagated small values and said propagated actual new values.

2. The method of claim 1, wherein the step of propagating small values includes the step of propagating nulls.

3. The method of claim 1, wherein the step of propagating small values includes the step of propagating small values for new values associated with unmodified fields.

4. The method of claim 1, wherein the step of propagating small values includes the step of propagating small values for old values associated with fields in a linked collection of unmodified fields.

5. The method of claim 1, wherein the step of propagating small values includes the step of propagating small values for old values associated with fields having been disabled for conflict detection.

6. The method of claim 1, wherein the step of detecting for a conflict within a corresponding record based on said propagated small values and said propagated actual old values includes the step of detecting for a conflict only for fields of said corresponding record associated with said propagated old values.

7. The method of claim 1, wherein the step of updating said corresponding record based on at least said propagated small values and said propagated actual new values includes the step of updating fields in said corresponding record associated with said propagated new values and said propagated old values.

8. A method of maintaining multiple copies of a body of data organized into records of related fields, said method comprising the computer-implemented steps of:

processing a request to perform an update to a record within a first copy of said body of data at a first site;

identifying which of the related fields of said record are unmodified fields and which of the related fields of said record are updated fields; and

propagating, to a second site storing a second copy of said body of data and capable of detecting conflicts therein, said update to said record by performing the steps of;

(a) propagating to said second site values of at least one of said related fields, said values being prior to said processing, as old values for said at least one of said related fields,

(b) propagating to said second site small values as new values for the unmodified fields, and

(c) propagating to said second site values of the updated fields subsequent to said processing as new values for the updated fields.

9. The method of claim 8, wherein the step of identifying which of the related fields of said record are unmodified fields and which of the related fields of said record are updated fields includes the step of identifying which of the related fields of said record are unmodified fields and which of the related fields of said record are updated fields based on said request to update said record.

10. The method of claim 8, wherein the step of identifying which of the related fields of said record are unmodified fields and which of the related fields of said record are updated fields includes the step of identifying which of the related fields are unmodified fields and which of the related fields are updated fields based on said old values and said new values.

11. The method of claim 8, further comprising the step of:

generating flag values for said fields, respectively, each of said flag values indicating whether or not a corresponding one of said fields is one of said updated fields;

wherein the step of propagating, to said second site, said update to said record includes the step of propagating said flag values to said second site.

12. The method of claim 8, wherein the step of (a) propagating to said second site values of at least one of said related fields, said values being prior to said processing, as old values for said at least one of said related fields includes the step of propagating values to said second site of all of said related fields prior to said processing as old values of all of said related fields.

13. The method of claim 8, further comprising the step of partitioning said record into a plurality of groups of said fields;

wherein the step of (a) propagating to said second site values of at least one of said related fields, said values being prior to said processing, as old values for said at least one of said related fields includes the steps of;

propagating to said second site values of fields in a same group as updated fields, said values being prior to said processing, as old values for said fields in said same group as updated fields; and

propagating to said second site small values of fields not in said same group as updated fields as old values for said fields not in said same group as updated fields.

14. The method of claim 8, further comprising the step of storing administrative flags for each of said fields;

wherein the step of (a) propagating to said second site values of at least one of said related fields, said values being prior to said processing, as old values for said at least one of said related fields includes the step of propagating to said second site small values as old values for fields indicated by said administrative flags.

15. The method of claim 8, wherein the step of (a) propagating to said second site values of at least one of said related fields, said values being prior to said processing, as old values for said at least one of said related fields includes the step of propagating to said second site a value at least a gigabyte in size as an old value for one of said unmodified fields.

16. The method of claim 8, wherein the step of (b) propagating to said second site small values as new values for the unmodified fields includes the step of propagating to said second site null values as said new values for the unmodified fields.

17. The method of claim 8, wherein said body of data is organized into rows and columns.

18. A method of maintaining multiple copies of a body of data organized into records of related fields, said method comprising the computer-implemented steps of:

partitioning said record into a plurality of groups of said fields;

processing a request to perform an update to a record within a first copy of said body of data at a first site;

identifying which of the groups are unmodified groups and which of the groups are updated groups, wherein all fields of an unmodified group are not modified and at least one field is an updated group is updated, and

propagating, to a second site storing a second copy of said body of data and capable of detecting conflicts therein, said update to said record by performing the steps of;

(a) propagating to said second site values of at least one field in an updated group, said values being prior to said processing, as old values for said at least one field in said updated group,

(b) propagating to said second site small values as old values for fields in an unmodified group,

(c) propagating to said second site values of one or more fields in an updated group, said values being subsequent to said processing as new values for said one or more fields in said updated group, and

(d) propagating to said second site small values as new values for said fields in an unmodified group.

19. The method of claim 18, wherein the step of identifying which of the groups are unmodified groups and which of the groups are updated groups includes the step of identifying which of the groups are unmodified groups and which of the groups are updated groups based on said request to update said record.

20. The method of claim 18, wherein the step of identifying which of the groups are unmodified groups and which of the groups are updated groups includes the step of identifying which of the groups are unmodified groups and which of the groups are updated groups based on said old values and said new values.

21. The method of claim 18, further comprising the step of identifying which of the related fields of said record are unmodified fields and which of the related fields of said record are updated fields;

wherein the step of (c) propagating to said second site values of one or more fields in an updated group, said values being subsequent to said processing, as new values for said one or more fields in said updated group includes the steps of;

(c1) propagating to said second site small values as new values for unmodified fields of said one or more of said fields in said group as updated fields, and

(c2) propagating to said second site values of the updated fields of said one or more of said fields in said group as updated fields as new values for the updated fields of said one or more of said fields in said group as updated fields.

22. The method of claim 21, further comprising the step of:

generating flag values for said fields, respectively, each of said flag values indicating whether or not a corresponding one of said fields is one of said updated fields;

wherein the step of propagating, to said second site, said update to said record includes the step of propagating said flag values to said second site.

23. The method of claim 18, wherein the step of (c) propagating to said second site values of one or more fields in an updated group, said values being subsequent to said processing, as new values for said one or more fields in said updated group includes the step of propagating to said second site said values of all said fields in said updated group as new values for all said fields in said updated group.

24. The method of claim 18, further comprising the step of storing administrative flags for each said fields;

wherein the step of propagating, to a second site storing a second copy of said body of data, said update to said record includes the step of propagating to said second site small values as old values for fields indicated by said administrative flags.

25. The method of claim 18, wherein said small values comprise null values.

26. The method of claim 18, wherein said body of data is organized into rows and columns.

27. A computer-readable medium bearing instructions for maintaining multiple copies of a body of data organized into records of related fields, said instructions arranged to cause one or more processors to perform the steps of:

processing a request to perform an update to a record within a first copy of said body of data at a first site;

identifying which of the related fields of said record are unmodified fields and which of the related fields of said record are updated fields; and

propagating, to a second site storing a second copy of said body of data and capable of detecting conflicts therein, said update to said record by performing the steps of;

(a) propagating to said second site values of at least one of said related fields, said values being prior to said processing as old values for said at least one of said related fields,

(b) propagating to said second site small values as new values for the unmodified fields, and

(c) propagating to said second site values of the updated fields subsequent to said processing as new values for the updated fields.

28. The computer-readable medium of claim 27, wherein the step of identifying which of the related fields of said record are unmodified fields and which of the related fields of said record are updated fields includes the step of identifying which of the related fields of said record are unmodified fields and which of the related fields of said record are updated fields based on said request to update said record.

29. The computer-readable medium of claim 27, wherein the step of identifying which of the related fields of said record are unmodified fields and which of the related fields of said record are updated fields includes the step of identifying which of the related fields are unmodified fields and which of the related fields are updated fields based on said old values and said new values.

30. The computer-readable medium of claim 27, wherein:

said instructions are further arranged to perform the step of generating flag values for said fields, respectively, each of said flag values indicating whether or not a corresponding one of said fields is one of said updated fields; and

the step of propagating, to said second site, said update to said record includes the step of propagating said flag values to said second site.

31. The computer-readable medium of claim 27, wherein the step of (a) propagating to said second site values of at least one of said related fields, said values being prior to said processing, as old values for said at least one of said related fields includes the step of propagating values to said second site of all of said related fields prior to said processing as old values of all of said related fields.

32. The computer-readable medium of claim 27, wherein:

said instructions are further arranged to perform the step of partitioning said record into a plurality of groups of said fields; and

the step of (a) propagating to said second site values of at least one of said related fields, said values being prior to said processing, as old values for said at least one of said related fields includes the steps of;

propagating to said second site values of fields in a same group as updated fields, said values being prior to said processing, as old values for said fields in said same group as updated fields; and

propagating to said second site small values of fields not in said same group as updated fields as old values for said fields not in said same group as updated fields.

33. The computer-readable medium of claim 27, wherein:

said instructions are further arranged to perform the step of storing administrative flags for each said fields; and

the step of (a) propagating to said second site values of at least one of said related fields, said values being prior to said processing, as old values for said at least one of said related fields includes the step of propagating to said second site small values as old values for fields indicated by said administrative flags.

34. The computer-readable medium of claim 27, wherein the step of (a) propagating to said second site values of at least one of said related fields, said values being prior to said processing, as old values for said at least one of said related fields includes the step of propagating to said second site a value at least a gigabyte in size as an old value for one of said unmodified fields.

35. The computer-readable medium of claim 27, wherein the step of (b) propagating to said second site small values as new values for the unmodified fields includes the step of propagating to said second site null values as said new values for the unmodified fields.

36. The computer-readable medium of claim 27, wherein said body of data is organized into rows and columns.

37. A computer-readable medium bearing instructions for maintaining multiple copies of a body of data organized into records of related fields, said instructions arranged for causing one or more processors to perform steps of:

partitioning said record into a plurality of groups of said fields;

processing a request to perform an update to a record within a first copy of said body of data at a first site;

identifying which of the groups are unmodified groups and which of the groups are updated groups, wherein all fields of an unmodified group are not modified and at least one field is an updated group is updated; and

propagating, to a second site storing a second copy of said body of data and capable of detecting conflicts therein, said update to said record by performing the steps of;

(a) propagating to said second site values of at least one field in an updated group, said values being prior to said processing, as old values for said at least one field in said updated group,

(b) propagating to said second site small values as old values for fields in an unmodified group,

(c) propagating to said second site values of one or more fields in an updated group, said values being subsequent to said processing, as new values for said one or more fields in said updated group, and

(d) propagating to said second site small values as new values for said fields in an unmodified group.

38. The computer-readable medium of claim 37, wherein the step of identifying which of the groups are unmodified groups and which of the groups are updated groups includes the step of identifying which of the groups are unmodified groups and which of the groups are updated groups based on said request to update said record.

39. The computer-readable medium of claim 37, wherein the step of identifying which of the groups are unmodified groups and which of thc groups are updated groups includes the step of identifying which of the groups are unmodified groups and which of the groups are updated groups based on said old values and said new values.

40. The computer-readable medium of claim 37, wherein:

said instructions are further arranged for performing the step of identifying which of the related fields of said record are unmodified fields and which of the related fields of said record are updated fields; and

the step of (c) propagating to said second site values of one or more fields in an updated group, said values being subsequent to said processing, as new values for said one or more fields in said updated group includes the steps of;

(c1) propagating to said second site small values as new values for unmodified fields of said one or more of said fields in said group as updated fields, and

(c2) propagating to said second site values of the updated fields of said one or more of said fields in said group as updated fields as new values for the updated fields of said one or more of said fields in said group as updated fields.

41. The computer-readable medium of claim 40, wherein:

said instructions are further arranged for performing the step of generating flag values for said fields, respectively, each of said flag values indicating whether or not a corresponding one of said fields is one of said updated fields; and

the step of propagating, to said second site, said update to said record includes the step of propagating said flag values to said second site.

42. The computer-readable medium of claim 37, wherein the step of (c) propagating to said second site values of one or more fields in an updated group, said values being subsequent to said processing, as new values for said one or more fields in said updated group includes the step of propagating to said second site said values of all said fields in said updated group as new values for all said fields in said updated group.

43. The computer-readable medium of claim 37, wherein:

said instructions are further arranged for performing the step of storing administrative flags for each said fields; and

the step of propagating, to a second site storing a second copy of said body of data, said update to said record includes the step of propagating to said second site small values as old values for fields indicated by said administrative flags.

44. The computer-readable medium of claim 37, wherein said small values are null values.

45. The computer-readable medium of claim 37, wherein said body of data is organized into rows and columns.