Method and apparatus for representing deleted data in a synchronizable database

• US 7,130,871 B2
• Filed: 10/17/2002
• Issued: 10/31/2006
• Est. Priority Date: 10/17/2002
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gengler, William Harold, Acree, Richard Kevin, Eagle, Brian Lee White, Paterson, Roy
• Primary Examiner(s): Pardo, Thuy N.
• Application Number:
  US10/273,591
• Publication Number:
  US 20040078393A1
• Time in Patent Office: 1,475 Days
• Field of Search: 707/101, 707/201, 707/204, 707/8, 707/10, 707/102, 707/103.R, 707/104.1, 707/203, 707/202, 707/205, 707/206, 717/171
• US Class Current: 707/621
• 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 16/275 Synchronous replication
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability
• CPC Class Codes: Y10S 707/99954 Version management

Abstract

A method, apparatus, and computer instructions for synchronizing a database used by a client device with at least one server. A locally unique identifier is associated with each record in the database at the client. The locally unique identifier for a deleted record is changed to a selected value. This value is selected in a manner to indicate that a record has been deleted. This locally unique identifier may be a negative value and may be selected by multiplying the locally unique identifier by a negative one. The selected value is used in synchronizing the database and is used to track records deleted since a last synchronization of the database. In the depicted examples, this selected value is unique and allows for mapping back to the locally unique identifier for the record.

Claims

1. A method for synchronizing a database used by a client device with at least one server, the method comprising:

associating locally unique identifier with each record in the database; and

changing a locally unique identifier for a deleted record to a negative value selected to indicate that a record has been deleted, wherein the negative value is used to track records deleted since a last synchronization of the database.

2. The method of claim 1, wherein the negative value is generated by multiplying the locally unique identifier by a negative one.

3. The method of claim 2 further comprising:

retrieving only records with positive locally unique identifier from the database.

4. The method of claim 2 further comprising:

removing a record having a negative locally unique identifier if a change identifier is less than or equal to all existing anchors.

5. The method of claim 1, wherein the client device is one of a personal digital assistant, a server, personal computer, and a mobile phone.

6. The method of claim 1, wherein the database is synchronized with a second database located on a data processing system.

7. The method of claim 2 further comprising:

returning the negative value to a positive value to undelete the deleted record.

8. A data processing system for synchronizing a database used by a client device with at least one server, the data processing system comprising:

a bus system;

a communications unit connected to the bus system;

a memory connected to the bus system, wherein the memory includes a set of instructions; and

a processing unit connected to the bus system, wherein the processing unit executes the set of instructions to associate a locally unique identifier with each record in the database; and

change a locally unique identifier for a deleted record to a negative value selected to indicate that a record has been deleted in which the negative value is used to track records deleted since a last synchronization of the database.

9. A data processing system for synchronizing a database used by a client device with at least one server, the data processing system comprising:

associating means for associating a locally unique identifier with each record in the database; and

changing means for changing a locally unique identifier for a deleted record to a negative value selected to indicate that a record has been deleted, wherein the negative value is used to track records deleted since a last synchronization of the database.

10. The data processing system of claim 9, wherein the negative value is generated by multiplying the locally unique identifier by a negative one.

11. The data processing system of claim 10 further comprising:

retrieving means for retrieving only records with a positive locally unique identifier from the database.

12. The data processing system of claim 10 further comprising:

removing means for removing a record having a negative locally unique identifier if a change identifier is less than or equal to all existing anchors.

13. The data processing system of claim 9, wherein the client device is one of a personal digital assistant a server, personal computer, and a mobile phone.

14. The data processing system of claim 9, wherein the database is synchronized with a second database located on a data processing system.

15. The data processing system of claim 10 further comprising:

returning means for returning the negative value to a positive value to undelete the deleted record.

16. A method for synchronizing a database used by a client device with at least one server, the method comprising:

associating a locally unique identifier with each record in the database, wherein the locally unique identifier uniquely Identifies the record in the database that it is associated with, and wherein a given locally unique identifier is used to access a given record that it is associated with during normal database access; and

changing the given locally unique identifier for the given record to a selected value selected to indicate that a record has been deleted, wherein the selected value is used in synchronizing the database with the at least one server.

17. A computer program product in a computer readable medium for synchronizing a database used by a client device with at least one server, the computer program product comprising:

first instructions for associating a locally unique identifier with each record in the database; and

second instructions for changing a locally unique identifier for a deleted record to a negative value selected to indicate that a record has been deleted, wherein the negative value is used to track records deleted since a last synchronization of the database.

18. A method for synchronizing a database used by a client device with at least one server, the method comprising:

associating a locally unique identifier with each record in the database; and

changing a locally unique identifier for a deleted record to a negative value selected to indicate that a record has been deleted, wherein the negative value is used to track records deleted since a last synchronization of the database and wherein the negative value is generated by multiplying the locally unique identifier by a negative one; and

removing a record having a negative locally unique identifier if a change identifier is less than or equal to all existing anchors.

19. The method of claim 18 further comprising:

retrieving only records with a positive locally unique identifier from the database.

20. The method of claim 18, wherein the database is synchronized with a second database located on a data processing system.