Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1994-08-05
2002-09-24
Von Buhr, Maria N. (Department: 2125)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000
Reexamination Certificate
active
06457007
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a distributed database management system having a plurality of information processors connected to a network.
Recently, database management systems for holding various data in common so as to use it effectively are introduced in many information processing systems.
Among them, a relational database management system for handling data in a related table format has come into wide use rapidly.
Conventional users construct a database on a main frame system and search or update common data. However, there are problems on cost, function, and operability imposed in a database management system of a main frame system.
Therefore, such a database management system of a main frame system is being changed to a client server type database management system using a miniature information processor such as a workstation or personal computer so as to decrease the cost of the system, to expand the function, to improve the operability, and to respond to the diversified information society flexibly. The client server type database management system can construct a highly expandable distributed database environment depending on the business scale.
A user connects an information processor which is a client to each database management system via a network and accesses a table on a relational database using a database access statement, for example, in the SQL (structured query language) which is the standard data manipulation language of the ISO (International Standardization Organization). In this case, it is necessary for the user in the distributed database environment to always recognize the database where the table to be accessed is stored, that is, the table location and to connect himself to an appropriate database before table access. Furthermore, it may be necessary to add the table location to each access statement. However, in a large scale distributed database environment, it is difficult for the user to recognize many table locations one by one and addition of the table location to each access statement requires a very complicated operation.
In the relational database, data in a plurality of related tables is searched by a database access statement and the tables can be joined as a table. This processing which is called a join is generally executed in a single database management system. In the distributed database environment, however, a join (distributed search function) for a plurality of tables stored in different database management systems is also necessary. However, a general client cannot be connected to a plurality of database management systems at the same time. Therefore, there is a product in which the database management system which receives a join request automatically fetches data from another database management system and joins it with the own search data so as to support the distributed search function. When such a distributed search function is used, it is necessary for the user to explicitly describe identification information for another database management system in which the table to be accessed is stored and user certification information at the time of connection in the database access statement.
To solve the above problems, it is important to allow the user in the distributed database environment not to be aware of the database management system where the table is stored, that is, to make the table position transparent.
As a method for realizing such a subject, there is a derivation database processing method which is described in Japanese Patent Application Laid-Open No. 4-112246. This method collects tables on a plurality of distributed database management systems partially and handles them as a derivation database and the user registers the definition information of each database management system and the definition information of the derivation database in a dictionary. The definition information of each database management system consists of identification information of a plurality of tables stored in each database and the definition information of the derivation database consists of identification information of a plurality of database management systems and tables which constitute the derivation database. The database manipulation means receives a derivation database access request from the application program, searches the above dictionary for the table location, and issues a database access statement to the database management system where the table is stored. By this method, the application program can access a plurality of database management systems via a derivation database.
By this derivation database processing method, the user can access a plurality of tables which are registered in the dictionary as a derivation database without being aware of the table location. However, when the user creates a new table after definition of the derivation database, it is necessary for the user to additionally define the created table and the stored identification information of the database management system in the dictionary.
In the distributed database environment, each department of enterprises often operates each database management system independently and accordingly there is a possibility that a duplicated table name exists between a plurality of database management systems. Since the aforementioned derivation database processing method identifies tables of the duplicated name uniquely, it is necessary to define a different name for each table.
In a general database environment, a new table is created frequently. Therefore, in the aforementioned derivation database processing method, it is necessary for the user to redefine the derivation database every time or to define a different name of the table and the operation burden is increased.
The database management system prevents an unqualified person from use of a database under the account control using the independent user ID (identifier: identification) and password (hereafter a combination of the two is called an account). The account control means installed in the database management system checks the password which is inputted by the user at the time of logging-in prior to table access, checks whether the logging-in user is granted a privilege for writing or reading in the table or record to be accessed, and then starts the table access processing.
However, in the distributed database environment where each database management system is operated independently, the accounts registered in the database management systems are not always the same. There is a method available for reregistering the accounts of all the database management systems and constructing a unified database account environment. However, for the reason of an increase in the account reregistration operation and reusing to the existing database application program property, many enterprises use a different account environment for each database management system continuously. Therefore, it is necessary for the user to selectively use the corresponding account for each database management system to be connected. However, in a large scale distributed database environment, in the same way as with the table location, storing and using of accounts to be used by the user for many database management systems require a very complicated operation.
SUMMARY OF THE INVENTION
An object of the present invention is to eliminate the difficulties of the prior arts mentioned above and to provide a distributed database management system which can correspond to a large scale distributed database environment by a simple operation without the table location being added to many access statements by the user.
Another object of the present invention is to provide a distributed database management system which can correspond to a large scale distributed database environment on the basis of single account information without a large amount of account information being stored and used by the user.
Another object of the present invention is to provide a distributed database management system which has
Hashimoto Hisashi
Ito Hiromichi
Kikuchi Satoshi
Nakane Keiichi
Nishiyama Eisaku
Antonelli Terry Stout & Kraus LLP
Hitachi , Ltd.
Von Buhr Maria N.
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