Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1999-12-03
2002-05-14
Corrielus, Jean M. (Department: 2772)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000, C707S793000, C455S432300, C455S419000, C455S435100, C455S466000, C455S556200, C455S410000, C455S517000, C370S349000, C340S870200
Reexamination Certificate
active
06389423
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
As for a data controlling method permitting a plurality of computers to share a data and to maintain copies of a shared data individually, the present invention relates to a data synchronization method for maintaining a consistency of the shared data among the plurality of computers.
2. Description of the Related Art
With the development of various types of mobile communication networks and general public networks accompanied by the dissemination of mobile information terminals, various mobile information terminal services can now be supplied. On one hand, an internet is also becoming popular. For this reason, needs such as “wanting to access the data of intranet through the internet” and “wanting to use a WEB service being supplied at the internet” from the mobile information terminals are emerging.
Use of the internet does not involve a cost of using the backbone. The data transfer using the internet is relatively stable. As well, the internet has a potential for a massive data transfer. On contrary, the data transfer using the public networks or the mobile communication networks are rather costly. Especially, the mobile communication networks have disadvantages such as potential for amount of data transfer is small, cutoff of the lines are frequent, and communication is comparatively high-priced.
In order to maintain the consistency of file data copies at a communication environment of high cost and limited potential in the data transferring, a technique disclosed in Japanese unexamined patent publication HEI9-244936 attempts to reduce a data communication traffic by exchanging only a difference generated by a data update.
A communication protocol known as TCP/IP is commonly being used at the internet. The TCP/IP is known as a connection type communication protocol. It configures a communication session between two nodes communicating with one another, and provides a highly reliable communication means. The disclosed technique also adopts the TCP/IP in its communication for maintaining the data consistency. Although the reliability of the communication improves by using the connection type communication protocol, however, use of the connection type communication protocol is disadvantaged that the communication would be limited to a pre-decided pair of two nodes.
The method of maintaining the data consistency by using the connection type communication protocol also has a disadvantage that the communication traffic increases in accordance with the increase in the number of data nodes should be synchronized. If there are more than three nodes even in the same subnet, the communication traffic multiplies based on the number of data synchronization line. Accordingly, this method has a disadvantage that the time taken in the data synchronization is increased as a whole, because of an exclusive use of the network.
The present invention, which relates to a data synchronization method for maintaining and controlling a replicated data, for example aims to supply a data synchronization method which reduces an increase in the communication traffic in comparison with an increase in the number of nodes where the data should be synchronized.
SUMMARY OF THE INVENTION
A data communication device of the present invention is the 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.
The data communication device of the present invention 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, 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.
The data communication device of the present invention 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).
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
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).
Th
Corrielus Jean M.
Mitsubishi Denki & Kabushiki Kaisha
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