Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1999-07-02
2002-03-12
Alam, Hosain T. (Department: 2172)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000, C707S793000, C707S793000, C709S230000, C714S002000, C714S006130, C714S012000, C714S015000, C714S016000, C714S019000, C714S020000
Reexamination Certificate
active
06356916
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a replica system and a method of producing a replica, by which a replica is produced among different databases and/or files.
2. Description of the Prior Art
Today, many computers are used in decentralized fashion and especially small-size computers are distributed to each department of a workplace. In such an environment, before starting business of the day, data necessary for databases or files of each distributed computer is customarily copied from a master database or master file on a host computer. After closing work of the day, revised data is copied into the host computer so as to update the master database or the master file.
As mobile computing technology has been developed, a user can use a computer outside his or her office, say at a customer's site or an employee's home. For example, when sales people start their operations of the day, they may copy necessary information from a master database or master file on a host computer to databases or files of their mobile computers. At the end of the day, these people transmit sales data and cost data to the host computer for updating the master database or master file on the host computer. This is the most effective method in terms of reduction of communication cost and access time.
Generally, a data exchange method and a system adopting this method are respectively referred to as a method of producing replica(s) and a replica system, in which data is copied between a plurality of databases and files.
FIG. 20
illustrates configuration of an existing replica system. In the figure, a replica system comprises a host computer
1001
and a distributed computer
1002
such as a mobile computer. The host computer
1001
and the distributed computer
1002
are connected together via a communication medium, say a LAN (local area network) or Internet.
The host computer
1001
has a master database A
1003
(master database is hereinafter referred to as “master DB”) and a master DB B
1004
, and also has a database management system A
1005
(database management system is hereinafter abbreviated to “DBMS”) and a DBMS B
1006
for managing each of the master DBs. It should be noted that these DBMS A
1005
and DBMS B
1006
may use either the same type of database programs or a different type of database programs.
The distributed computer
1002
consists of a copy database C
1007
(copy database is hereinafter referred to as “copy DB”) and a copy DB D
1008
used for copying necessary data from the master DB A
1003
, and consists of a DBMS C
1009
and a DBMS D
1010
which are database management systems for managing each of the copy DBs. DBMS C
1009
and DBMS D
1010
use the same type of database programs which are the same as those used by the DBMS A
1005
of the host computer.
A database replica program
1011
presets the correspondence between the master DBs of the host computer
1001
and the copy DBs of the distributed computer
1002
, and controls data copying between databases at user's request. This database replica program
1011
is located in the host computer
1001
.
The operation of the database replica program
1011
will be described below.
When the user requests a data copy from the master DB A
1003
to the copy DB C
1007
, data is read from the master DB A
1003
via the DBMS A
1005
and written into the copy DB C
1007
via the DBMS C
1009
. When the user requests a copy of the updated data from the copy DB C
1007
to the master DB A
1003
, the updated data is read from the copy DB C
1007
via the DBMS C
1009
. The data is then written into the master DB A
1003
via DBMS A
1005
.
Similarly, copying of data is performed between the master DB A
1003
and the copy DB D
1008
. However, the updated data in the copy DB D
1008
cannot be copied to the master DB B
1004
as shown in
FIG. 20
by a broken line if the DBMSs managing the copy DB D and the master DB B use different types of database programs. Even when the database programs are of the same type, copying is not available unless the correspondence between a copy DB and a master DB exists in the database replica program
1011
.
The host computer
1001
has a master file
1012
and a file replica program
1013
, while the distributed computer
1002
contains a copy file
1014
which corresponds to the master file
1012
.
Correspondence between the master file
1012
on the host computer
1001
and the copy file
1014
of the distributed computer
1002
is preset in the file replica program
1013
. The program then controls copying of data between the files at user's request.
Many types of database programs are now available in the market and they are specifically used according to their intended use. For example, a database management system using a database program such as DB2™ by IBM Corporation or Oracle 8™ by Oracle Corporation which are capable of processing many tasks at one time, in parallel, is suitable for a host computer which may be used by many people simultaneously. On the other hand, for computers for private-use, such as a mobile computer, where tasks are sequentially created, a database management system using a database program with less load, say Oracle light™ by Oracle Corporation or Access™ by Microsoft Corporation, is suitable.
However, in the conventional replica system, the database replica program is designed in correspondence with a specific database program. Therefore, the system cannot interface with a database management system Using different types of database programs. Accordingly, a master DB and a copy DB should be managed by a database management system which uses the same types of database programs. Management of this kind prevents a system construction from becoming a flexible one which operates conforming to a load.
When constructing a replica system which produces a replica between databases or between files, two types of program, namely, a database replica program and a file replica program are required. This requirement adds to the load on the system.
Furthermore, the database replica program must have all data necessary for copying, including data in tables of the copy DB and the master DB, thus making the system construction complicated. Particularly, the whole of the database replica program has to be modified each time a data format of the copy DB or copy file is added or converted, which makes the modification procedure very complicated.
In addition, when the user intends to add some additional function, such as a character code conversion, he or she has a difficult task, such as to modify the whole of the database replica program. Addition of such a function is therefore not feasible in actuality.
SUMMARY OF THE INVENTION
The present invention aims to solve the problems mentioned above. It is a primary object of this invention to provide a replica system with a less load, which can deal with a database management system including plural kinds of database programs and can deal with files.
It is another object of the present invention to provide a replica system to which a user can easily add or modify a data format of the copy DB or the copy file, as well as add a function, such as a character code conversion.
According to one aspect of the invention, the objects of the invention are achieved by a replica system having first data storage means, first data management means for managing the first data storage means, second data storage means, and second data management means for managing the second data storage means, wherein replica of data is produced between said first data storage means and said second data storage means; comprising, replica management means for receiving a replica instruction, and, according to the replica instruction, determining an object to be read from said first data storage means and an object to be written in said second data storage means, first interface means, giving a command to said first data management means, for reading from said first data storage means data ass
Ichikawa Noriko
Yamada Kouichi
Yamatari Mitsuyoshi
Alam Hosain T.
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
Truong Cam Y
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