Computer data sharing system and method for maintaining replica consistency

• US 6,571,278 B1
• Filed: 10/22/1999
• Issued: 05/27/2003
• Est. Priority Date: 10/22/1998
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Ahuja, Mohan, Negishi, Yasushi, Tago, Kazuya
• Primary Examiner(s): Barot, Bharat
• Application Number:
  US09/425,559
• Time in Patent Office: 1,313 Days
• Field of Search: 709/200-201, 709/203-205, 709/212, 709/216-219, 709/242, 709/245, 709/248, 707/201-204, 707/8, 707/10, 714/5-7, 711/141
• US Class Current: 709/213
• CPC Class Codes: H04L 67/62 Establishing a time schedule for servicing the requests
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

To improve communication efficiency during the updating of a replica, and to reduce the amount of memory required for the updating of a replica. The present invention is a computer for maintaining consistency of replica contents by interchanging data modification with another computer. The computer includes: a replica including shared data; a receiver for receiving, from another computer, a modification request for data included in the replica; and a controller for controlling, regardless of a receiving order of the modification request, for each receipt of the modification request, a timing of update execution for the replica in accordance with the received modification request by using information included in the modification request. The timing of replica updating in accordance with the received modification requests can be determined, regardless of the order in which the modification requests are received, that is, the order of the transmission from other computers. Therefore, communication efficiency can be improved and the amount of required memory can be reduced.

Claims

1. A computer for maintaining consistency of replica contents by interchanging data modification with another computer, said computer comprising:

a replica including shared data;

a receiver for receiving, from said another computer, a modification request for data included in said replica, wherein said modification request includes;

a designation indicating no restriction for a modification order;

a first designation indicating that after all modification requests preceding a current modification request have been affected by said replica, said replica is to be updated in accordance with said current modification request;

a second designation indicating that modification requests following a current modification request are to be affected by said replica after said replica has been updated in accordance with said current modification request;

or

a third designation indicating that after all modification requests preceding a current modification request have been affected by said replica, said replica is to be updated in accordance with said current modification request, and that all modification requests following said current modification request are to be affected by said replica after said replica has been updated in accordance with said current modification request; and

a controller for controlling, regardless of a receiving order of said modification request, for each receipt of said modification request, a timing of update execution for said replica in accordance with the received modification request by using information included in said modification request.

2. The computer according to claim 1, wherein said information included in said modification request further includes:

a first number of modification requests that have been generated and that include said second or third designation; and

a second number of modification requests that have been generated following the last modification request including said second or third designation.

3. The computer according to claim 2, wherein said controller stores first and second management values that respectively correspond to said first and second numbers and that define a timing of date execution for said replica.

4. The computer according to claim 2, wherein, if said replica is updated in accordance with said modification request, said controller stores, as third and fourth numbers, said first and second numbers included in said modification request.

5. The computer according to claim 4, further comprising a transmitter for transmitting to another computer a modification request for data in said replica, wherein said controller makes said third and fourth numbers to be included in said modification request.

6. A computer for maintaining consistency of replica contents by interchanging modification data with another computer, said computer comprising:

a replica including shared data;

means for instructing modification of data included in said replica, and for designating information concerning a modification order to the modification of data, wherein said information concerning said modification order includes;

a designation indicating no restriction for a modification order;

a first designation indicating that after all modification requests preceding a current modification request have been affected by said replica, said replica is to be updated in accordance with said current modification request;

a second designation indicating that modification requests following a current modification request are to be affected by said replica after said replica has been updated in accordance with said current modification request;

or

a third designation indicating that after all modification requests preceding a current modification request have been affected by said replica, said replica is to be updated in accordance with said current modification request, and that all modification requests following said current modification request are to be affected by said replica after said replica has been updated in accordance with said current modification request;

means for generating a modification request that corresponds to an instruction of the modification of data and includes information concerning said modification order; and

a transmitter for transmitting said modification request in such a manner that it is not confirmed that a generation order and a transmitting order of said modification request are identical.

7. The computer according to claim 6, wherein said modification request further includes:

a first number of modification requests that have been generated and that include said second or third designation; and

a second number of modification requests that have been generated following the last modification request including said second or third designation.

8. The computer according to claim 6, further comprising a receiver for receiving from another computer a modification request for data included in said replica, wherein the received modification request includes response information indicating that said replica has been updated by a destination computer in accordance with the transmitted modification request.

9. The computer according to claim 8, further comprising means for referring to said response information to determine whether said modification request that has been transmitted is to be deleted.

10. The computer according to claim 6, further comprising a controller for controlling, regardless of a receiving order said modification request, for each receipt of said modification request, a timing of update execution for said replica in accordance with said received modification request.

11. A method for maintaining consistency replica contents between computers, said method comprising:

a receiver in a first computer for receiving a modification request from a second computer for data included in a replica having shared data, wherein said modification request includes;

a designation indicating no restriction for a modification order;

a first designation indicating that after all modification requests preceding a current modification request have been affected by said replica, said replica is to be updated in accordance with said current modification request;

a second designation indicating that modification requests following a current modification request are to be affected by said replica after said replica has been updated in accordance with said current modification request;

or

a third designation indicating that after all modification requests preceding a current modification request have been affected by said replica, said replica is to be updated in accordance with said current modification request, and that all modification requests following said current modification request are to be affected by said replica after said replica has been updated in accordance with said current modification request; and

controlling regardless of a receiving order of said modification request, for each receipt of said modification request, a timing of update execution for said replica in accordance with the received modification request by using information included in said modification request.

12. The method according to claim 11, wherein said information included in said modification request further includes:

a first number of modification requests that have been generated and that include said second or third designation; and

a second number of modification requests that have been generated following the last modification request including said second or third designation.

13. The method according to claim 12, further comprising storing first and second management values that respectively correspond to said first and second numbers and that define a timing of update execution for said replica.

14. The method according to claim 12, wherein, if said replica is updated in accordance with said modification request, storing said first and second numbers included in said modification request as third and fourth numbers.

15. The method according to claim 14, further comprising transmitting to another computer a modification request for data in said replica, wherein said controller makes said third and fourth numbers to be included in said modification request.