Data synchronization between distributed computers

• US 20050080796A1
• Filed: 07/29/2004
• Published: 04/14/2005
• Est. Priority Date: 10/10/2003
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Midgley, Nicholas James
• Granted Patent: US 7,213,038 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/10 File systems; File servers
• CPC Class Codes: G06F 16/275 Synchronous replication
• CPC Class Codes: Y10S 707/99938 Concurrency, e.g. lock management in shared database
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

Apparatus, method and program for maintaining common data in first, second and third datasets in first, second and third respective computer systems. The first computer system is assigned a sole right to approve updates of the common data while able, and a second computer system is assigned a right to approve updates of the common data when the first computer system is unable. The third computer system subsequently makes a request to the first computer system to update the common data, and in response, the first computer system updates the common data in the first dataset and advises the second and third computer systems to make a corresponding update to their second and third datasets, respectively. The third computer system makes a subsequent request to the first computer system to update the common data, and in response, the third computer system learns that the first computer system is unable to approve updates of the common data and determines that the second computer system has a right to approve updates of the common data when the first computer system is unable to approve updates of the common data. In response, the third computer system makes a request to the second computer system to update the common data and notify the second computer system that the first computer system is unable to approve updates of the common data. The second computer system updates the common data in the second dataset and advises the third computer system to make a corresponding update to the third dataset.

Claims

1. A method for maintaining common data in first, second and third datasets in first, second and third respective computer systems, said method comprising the steps of:

assigning said first computer system a sole right to approve updates of said common data while said first computer system is able to approve updates of said common data, and assigning said second computer system a right to approve updates of said common data when said first computer system is unable to approve updates of said common data;

said third computer system subsequently making a request to said first computer system to update said common data, and in response, said first computer system updating said common data in said first dataset and advising said second and third computer systems to make a corresponding update to their second and third datasets, respectively;

said third computer system making a subsequent request to said first computer system to update said common data, and in response, said third computer system learning that said first computer system is unable to approve updates of said common data and determining that said second computer system has a right to approve updates of said common data when said first computer system is unable to approve updates of said common data, and in response, said third computer system making a request to said second computer system to update said common data and notifying said second computer system that said first computer system is unable to approve updates of said common data or that said second computer system has the right to approve updates of said common data; and

in response to said notification, said second computer system updating said common data in said second dataset and advising said third computer system to make a corresponding update to said third dataset.

2. A method as set forth in claim 1 wherein said third computer system maintains a table indicating that said first computer system has the sole right to update said common data when able and said second computer system has the right to update said common data when said first computer system is unable to update said common data.

3. A method as set forth in claim 2 wherein said table also indicates that said second computer system has the sole right to update said common data when said first computer system is unable to update said common data.

4. A method as set forth in claim 1 wherein said second computer system has the sole right to update said common data when said first computer system is unable to update said common data.

5. A method as set forth in claim 1 wherein each of said computer systems communicates with each of the other computer systems via a network.

6. A method as set forth in claim 5 wherein said network is the Internet, and said common data can be accessed by a user via a web browser.

7. A method as set forth in claim 1 wherein:

the assigning steps are performed by assigning a first program within said first computer system the sole right to update said common data while said first computer system is able to update said common data, and assigning a second program within said second computer system the right to update said common data when said first computer system is unable to update said common data.

8. A method as set forth in claim 7 wherein said first program is part of a first middleware program within said first computer system, said second program is part of a second middleware program within said second computer system, and said third program is part of a third middleware program within said third computer system.

9. A method as set forth in claim 8 wherein said first dataset is managed by a database manager program of a first type and said second dataset is managed by a database manager program of a second, different type, such that said first database manager program would be incompatible with said second database manager program without said first or second middleware program to act as a protocol interface.

10. A method as claimed in claim 1 wherein said first computer system maintains a log of most often performed queries for said common data.

11. A method as claimed in claim 10 wherein said first computer system notifies said second computer system of said most often performed queries for said common data.

12. A method as set forth in claim 11 wherein in response to said notification from said first computer system of said most often performed queries, said second computer system caches the common data which is subject of said most often performed queries.

13. A distributed computer system for maintaining common data in first, second and third datasets in first, second and third respective computer systems, said distributed computer system comprising:

said first computer system including means for assigning a sole right to approve updates of said common data while said first computer system is able to approve updates of said common data, and assigning said second computer system a right to approve updates of said common data when said first computer system is unable to approve updates of said common data;

said third computer system including means for subsequently making a request to said first computer system to update said common data, and in response, said first computer system including means for updating said common data in said first dataset and advising said second and third computer systems to make a corresponding update to their second and third datasets, respectively;

said third computer system including means for making a subsequent request to said first computer system to update said common data, and in response, said third computer system including means for learning that said first computer system is unable to approve updates of said common data and determining that said second computer system has a right to approve updates of said common data when said first computer system is unable to approve updates of said common data, and in response, said third computer system including means for making a request to said second computer system to update said common data and notifying said second computer system that said first computer system is unable to approve updates of said common data or that said second computer system has the right to approve updates of said common data; and

in response to said notification, said second computer system including means for updating said common data in said second dataset and advising said third computer system to make a corresponding update to said third dataset.

14. A computer program product for maintaining common data in first, second and third datasets in first, second and third respective computer systems, said computer program product comprising:

one or more computer readable medium;

first program instructions for execution within said first computer system to assign a sole right to approve updates of said common data while said first computer system is able to approve updates of said common data, and assign said second computer system a right to approve updates of said common data when said first computer system is unable to approve updates of said common data;

second program instructions for execution within said third computer system to subsequently make a request to said first computer system to update said common data, and in response, third program instructions for execution within said first computer system to update said common data in said first dataset and advise said second and third computer systems to make a corresponding update to their second and third datasets, respectively;

fourth program instructions for execution within said third computer system to make a subsequent request to said first computer system to update said common data, and in response, fifth program instructions for execution within said third computer system to learn that said first computer system is unable to approve updates of said common data and determine that said second computer system has a right to approve updates of said common data when said first computer system is unable to approve updates of said common data, and in response, sixth program instructions for execution within said third computer system to make a request to said second computer system to update said common data and notify said second computer system that said first computer system is unable to approve updates of said common data or that said second computer system has the right to approve updates of said common data; and

in response to said notification, seventh program instructions for execution within said second computer system to update said common data in said second dataset and advise said third computer system to make a corresponding update to said third dataset; and

wherein

said first, second, third, fourth, fifth, sixth and seventh program instructions being recorded on said one or more computer readable medium.

15. A method for maintaining common data in first and second datasets in first and second respective computer systems, said method comprising the steps of:

assigning said first computer system a sole right to approve updates of said common data while said first computer system is able to approve updates of said common data, and assigning said second computer system a right to approve updates of said common data when said first computer system is unable to approve updates of said common data;

said second computer system subsequently making a request to said first computer system to update said common data, and in response, said first computer system updating said common data in said first dataset and advising said second computer system to make a corresponding update to said second dataset;

said second computer system making a subsequent request to said first computer system to update said common data, and in response, said second computer system learning that said first computer system is unable to approve updates of said common data and determining that said second computer system has a right to approve updates of said common data when said first computer system is unable to approve updates of said common data, and in response, said second computer system updating said common data in said second data set corresponding to said subsequent request.

16. A method as set forth in claim 15 wherein subsequently said first computer system being able to update said common data in said first data set, and said second computer learning that said first computer is able to update said common data in said first data set and notifying said first computer system to update said common data in said first dataset corresponding to said subsequent request.

17. A method as set forth in claim 15 further comprising the subsequent step of said second computer notifying said first computer system to update said common data in said first dataset corresponding to said subsequent request.