Relational database synchronization method and a recording medium storing a program therefore

• US 6,374,262 B1
• Filed: 09/01/1998
• Issued: 04/16/2002
• Est. Priority Date: 03/25/1998
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Kodama, Michiteru
• Primary Examiner(s): Alam, Hosain T.
• Assistant Examiner(s): FLEURANTIN, JEAN B
• Application Number:
  US09/145,030
• Time in Patent Office: 1,323 Days
• Field of Search: 707/1, 707/200, 707/201, 714/12, 714/14
• US Class Current: 707/623
• 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 707/954 Relational
• CPC Class Codes: Y10S 707/99952 Coherency, e.g. same view to multiple users

Abstract

A relational database synchronization method for synchronizing master data with data of replica machines, which data is updated usually with the replica machines disconnected from a master machine, so that there may be no inconsistency among the data. After a replica machine is connected to the master machine via a network at an arbitrary time, it extracts records of which the day of last update is later than a master differential extraction completion time, from replica data as replica differentials, and the master machine extracts records of which the replica differential reflection time is later than the master differential extraction completion time, from the master data as master differentials, updates the master differential extraction completion time to the current time, and causes the replica differentials to be reflected in the master data. The replica machine then causes the master differentials to be reflected in the replica data and updates the master differential extraction completion time. This completes the synchronization process and the connection with the master machine may be cut off thereafter at an arbitrary time.

Claims

1. A relational database synchronization method for synchronizing master data of a relational database held by a master machine with replica data which is a duplication of the master data and is held by each of a large number of replica machines, each replica machine usually operating with use of the replica data while in an off-line state with respect to the master machine, said relational database synchronization method comprising:

connecting a replica machine to the master machine at an arbitrary time to make a request for synchronization;

extracting, in said replica machine, a record of which a day of last update is later than a master differential extraction completion time, from the replica data as a replica differential;

transferring the extracted replica differential to the master machine;

extracting, in the master machine, a record of which a replica differential reflection time is later than a master differential extraction completion time, as a master differential from the master data with reference to records held by said replica machine which has made the request for synchronization, and updating the master differential extraction completion time to a current time;

causing the replica differential to be reflected in the master data;

transferring the master differential and the updated master differential extraction completion time to said replica machine;

causing the master differential transferred from the master machine to be reflected in the replica data in said replica machine, and updating the master differential extraction completion time held by said replica machine to the transferred master differential extraction completion time; and

cutting off the connection between said replica machine and the master machine.

2. The relational database synchronization method according to claim 1, wherein the master data and the replica data each comprise a table to be synchronized, and a duplication management table.

3. The relational database synchronization method according to claim 2, wherein the duplication management table stores a user number for identifying said replica machine, a group number for identifying a group including two or more of the replica machines, and the master differential extraction completion time.

4. The relational database synchronization method according to claim 2, wherein the table to be synchronized stores a user number for identifying said replica machine, a group number for identifying a group including two or more of the replica machines, the day of last update on which a record was updated in said replica machine, a deletion flag for recording deletion made in said replica machine, the replica differential reflection time, and an auxiliary main-key serving as a main-key for uniquely specifying a user when combined with the user number.

5. A relational database synchronization method for synchronizing master data of a relational database held by a master machine with replica data which is a duplication of the master data and is held by each of a large number of replica machines, each replica machine usually operating with use of the replica data while in an off-line state with respect to the master machine, said relational database synchronization method comprising:

connecting a replica machine to the master machine at an arbitrary time to make a request for synchronization;

extracting, in said replica machine, a record of which a day of last update is later than a master differential extraction completion time, from the replica data as a replica differential;

transferring the extracted replica differential to the master machine;

registering said replica machine which has made the request for synchronization, in a master differential extraction queue in the master machine;

registering said replica machine which has made the request for synchronization, in a replica differential reflection queue in the master machine;

extracting a record of which a replica differential reflection time is later than a master differential extraction completion time, as a master differential from the master data with reference to records held by said replica machine which has made the request for synchronization and updating the master differential extraction completion time to a current time when a turn for said replica machine has come in the master differential extraction queue;

transferring the master differential and the updated master differential extraction completion time to said replica machine;

cutting off the connection between said replica machine and the master machine;

causing the master differential transferred from the master machine to be reflected in the replica data in said replica machine, and updating the master differential extraction completion time held by said replica machine to the transferred master differential extraction completion time; and

causing the replica differential to be reflected in the master data when a turn for said replica machine which made the request for synchronization has come in the replica differential reflection queue.

6. The relational database synchronization method according to claim 5, wherein the master data and the replica data each comprise a table to be synchronized, and a duplication management table.

7. The relational database synchronization method according to claim 6, wherein the duplication management table stores a user number for identifying said replica machine, a group number for identifying a group including two or more of the replica machines, and the master differential extraction completion time.

8. The relational database synchronization method according to claim 6, wherein the table to be synchronized stores a user number for identifying said replica machine, a group number for identifying a group including two or more of the replica machines, the day of last update on which a record was updated in said replica machine, a deletion flag for recording deletion made in said replica machine, the replica differential reflection time, and an auxiliary main-key serving as a main-key for uniquely specifying a user when combined with the user number.

9. The relational database synchronization method according to claim 5, wherein said causing the replica differential to be reflected in the master data is executed by batch processing at night.

10. A computer-readable recording medium storing a relational database synchronization program which includes master differential extracting means for extracting a record of which a replica differential reflection time is later than a master differential extraction completion time, as a master differential from master data of a relational database of a master machine with reference to records of replica data held by a replica machine which has made a request for synchronization, and for updating the master differential extraction completion time to a current time, master differential transferring means for transferring the master differential and the updated master differential extraction completion time to the replica machine, master differential reflecting means for causing the master differential transferred by said master differential transferring means to be reflected in the replica data and for updating the master differential extraction completion time held by the replica machine to the transferred master differential extraction completion time, replica differential extracting means for extracting a record of which a day of last update is later than the master differential extraction completion time, from the replica data as a replica differential, replica differential transferring means for transferring the replica differential extracted by said replica differential extracting means to the master machine, replica differential reflecting means for causing the replica differential transferred by said replica differential transferring means to be reflected in the master data, and queue processing means for managing order of execution of said master differential extracting means and said replica differential reflecting means.