Data synchronization method for maintaining and controlling a replicated data

• US 6,389,423 B1
• Filed: 12/03/1999
• Issued: 05/14/2002
• Est. Priority Date: 04/13/1999
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Sakakura, Takashi
• Primary Examiner(s): Corrielus, Jean M.
• Application Number:
  US09/453,229
• Time in Patent Office: 893 Days
• Field of Search: 455/432, 455/419, 455/435, 455/466, 455/552, 455/410, 455/517, 370/349, 340/870.2, 707/10, 707/203, 707/206
• US Class Current: 707/613
• 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 707/922 Communications
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

The aim of the present invention is, as for a data communication among the nodes sharing, managing and maintaining the replicated data, to reduce the communication traffic by utilizing attributes of individual communication media. The application program of the node on the transmitting side inserts the data object into the data store, and the data synchronizer transmits an update message including the differential data and the log number. The node on the receiving side compares the log number of the update log data of its node and the log number of the update message it has received, and decides whether or not to adopt the update message.

Claims

1. A data communication device connected to a communication mechanism which connects to another data communication device, comprising:

a shared data storing unit for storing a shared data replicated and managed by the data communication device and the another data communication device;

a shared data updating unit for updating the shared data stored in the shared data storing unit;

a version managing unit for storing and managing a version of the shared data;

a version communication unit for communicating the version of the shared data by using the communication mechanism;

an update data communication unit for communicating a update data which is a differential data between the shared data before updating and the shared data after updating by using the communication mechanism;

wherein the data communication device executes a plurality of processes as a transmitting side data communication device when the shared data updating unit updates the shared data stored in the shared data storing unit (case (1)), the plurality of processes includes

a process A by the version managing unit, for creating the version of the shared data updated by the shared data updating unit and storing the created version;

a process B by the version communication unit, for transmitting the version stored in the version managing unit; and

a process C by the update data communication unit, for transmitting the update data which is a differential data between the shared data before updating and the shared data after updating;

wherein the data communication device executes a plurality of processes as a receiving side data communication device when the another data communication device updates the shared data stored in the another data communication device (case (2)), the plurality of processes includes;

a process D by the version communication unit, for receiving the version transmitted from the another data communication device;

a process E by the update data communication unit, for receiving the update data transmitted from the another data communication device;

a process F by the version managing unit, for deciding whether to apply the update data based on the version stored in the version managing unit and the version received by the version communication unit, and for storing the received version when the version managing unit decides to apply the update data;

a process G by the shared data storing unit, for storing the update received data when the version managing unit decides to apply the update data.

2. The data communication device according to claim 1,

wherein the data communication device executes a process H by the version communication unit, for transmitting the version stored in the version managing unit, in the case (2), in addition to the processes of D to G, as the receiving side data communication device,

wherein the data communication device executes a process I by the version communication unit, for receiving the version of the shared data transmitted by the another data communication device, and

a process J by the version managing unit for storing the version of the shared data received by the version communication unit with an identification information of the another data communication device, in the case (1), in addition to the process of A to C, as the transmitting side data communication device.

3. The data communication device according to claim 1,

wherein the data communication device stores identification information of the another data communication device and identifies the another data communication device by the stored identification information,

wherein the version communication unit as a part of the transmitting side data communication device transmits the created version to the identified another data communication device in the process B when the shared data updating unit updates the shared data stored in the shared data storing unit in the case (1), and

wherein the update data communication unit as a part of the transmitting side data communication device transmits the update data to the identified another data communication device in the process C when the shared data updating unit updates the shared data stored in the shared data storing unit in the case (1).

4. The data communication device according to claim 1,

wherein the version communication unit as a part of the receiving side data communication device intercepts the version transmitted from the another data communication device in the process D when the another data communication device updates the shared data stored in the another data communication device in the case (2), and

wherein the update data communication unit as a part of the receiving side data communication device intercepts the update data transmitted from the another data communication device in the process E when the another data communication device updates the shared data stored in the another data communication device in the case (2).

5. The data communication device according to claim 1 further comprising a mode controlling unit for switching to a mode of declaring data sharing and a data update commencement message communication unit for communicating a message for commencing data update by using the communication mechanism,

wherein the data update commencement message communication unit as a part of the receiving side communication device executes a process of transmitting the message for commencing data update when the shared data updating unit updates the shared data stored in the shared data storing unit in the mode of declaring data sharing,

wherein the version managing unit omits the process A of creating the version of the shared data updated by the shared data updating unit and storing the created version and the version communicating unit omits the process B of transmitting the version stored in the version stored in the version managing unit when the shared data updating unit updates the shared data stored in the shared data storing unit in the mode of declaring data sharing in the case (1),

wherein the shared data updating unit as a part of the receiving side communication device by itself stops updating the shared data stored in the shared data storing unit when the data update commencement message communication unit receives the message for commencing data update in the mode of declaring data sharing,

wherein the version communication unit omits the process D of receiving the version transmitted from the another data communication device and the version managing unit omits the process F of deciding whether to apply the update data and storing the received version when the another data communication device updates the shared data stored in the another data communication device in the mode of declaring data sharing in the case (2),

wherein in the process G the shared data storing unit all the time stores the update data received when the another data communication device updates the shared data stored in the another data communication device in the mode of declaring data sharing in the case (2), and

wherein the version managing unit creates the version of the shared data updated and stores the created version when the mode controlling unit releases the mode of declaring data sharing.

6. The data communication device according to claim 1 further comprising a mode controlling unit for switching to a mode of declaring data sharing and a data update commencement message communication unit for communicating a message for commencing data update by using the communication mechanism,

wherein the shared data updating unit as a part of the receiving side communication device by itself stops updating the shared data stored in the shared data storing unit when the data update commencement message communication unit receives the message for commencing data update outside the mode of declaring data sharing and,

wherein the processes of D to G are not implemented when the another communication device updates the shared data stored in the another data communication device outside the mode of declaring data sharing.

7. The data communication device according to claim 1,

wherein the communication mechanism connecting a plurality of other data communication devices have a multicast communication function,

wherein the data communication device stores a identification information of the plurality of other data communication devices and identifies the plurality of other data communication devices by the stored identification information,

wherein the version communication unit as a part of the transmitting side data communication device transmits in multicast the created version to the plurality of identified other data communication devices in the process B when the shared data updating unit updates the shared data stored in the shared data storing unit,

wherein the update data communication unit as a part of the transmitting side data communication device transmits in multicast the created update data to the plurality of identified other data communication devices in the process C when the shared data updating unit updates the shared data stored in the shared data storing unit,

wherein the version communication unit receives the version of the shared data transmitted from the plurality of identified other data communication devices, and

wherein the version managing unit stores the version of the shared data received by the version communication unit with the identification information of the plurality of other data communication devices which transmit the version.

8. The data communication device according to claim 7 further comprising a media access control unit for confirming no data received during a pre-determined time,

wherein the version communication unit as a part of transmitting side data communication device transmits in multicast the created version to the plurality of identified other data communication devices after the media access control unit confirming no data received during the pre-determined time in the process B when the shared data updating unit updates the shared data stored in the shared data storing unit in the case (1),and

wherein the update data communication unit as a part of the transmitting side data communication device transmits in multicast the update data to the plurality of identified other data communication devices after the media access control unit confirming no data received during the pre-determined time in the process C when the shared data updating unit of one data communication device updates the shared data stored in the shared data storing unit in the case (1).

9. The data communication device according to claim 1,

wherein the communication mechanism connecting a plurality of other data communication devices have a multicast communication function,

wherein the data communication device stores identification information of the plurality of other data communication devices and identifies the plurality of other data communication devices by the stored identification information, and

wherein the data communication device further executes;

a process K by the version communication unit, for transmitting in multicast the version stored in the version managing unit to the plurality of identified other communication devices; and

a process L by the update data communication unit, for transmitting in multicast the updated data stored in the shared data storing unit to the plurality of identified other communication devices.

10. The data communication device according to claim 1,

wherein the communication mechanism includes more than two types of communication mechanisms,

wherein the version communication unit can communicate the version of the shared data by using either one of more than two types of communication mechanisms,

and wherein the update data communicating unit can communicate the update data by using either one of more than two types of communication mechanisms.

11. The data communication device according to claim 10,

wherein the version communication unit and the update data communication unit selects a pre-determined communication mechanism, and communicate by using the selected communication mechanism.

12. The data communication device according to claim 5,

wherein the mode controlling unit switches to a mode of declaring data sharing by linking with the another data communication device prior to the processes of the receiving side data communication device even if the another data communication device updates the data stored in the another data communication device.