JPH1011342A - Method and device for access to data base system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the access method for the data base system which makes it possible to easily generate a program for the exclusive control, state change information, and consistency maintenance of a data base. SOLUTION: A data base class holding exclusive information 2, state change information 3, consistency information 4, etc., as static member data is stored in a data base class storage means 1, and a data base control means 2 performs control over the data base such as exclusive control 6, state change information 7, and consistency control 8 by referring to the static member data stored in the data base class storage means 1 according to data base instances.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an access method and an access apparatus for a database system, and more particularly to an access method and an access apparatus suitable for exclusive control of a database, notification of status change, or maintenance of database consistency. It is.

[0002]

2. Description of the Related Art In a conventional database system, information used in various fields is normalized and stored, thereby enabling information disclosure under various search conditions.

In order to use the database system widely and effectively by an unspecified number of users, a large-scale system using a computer and a network is constructed as shown in FIG. By processing a large amount of data at high speed, the client 33
35 can freely delete, add, or publish information stored in the database 32 via the server 31.

In order to realize this database system using a computer and a network, the following has been performed. First, many users issue access requests such as reference, write, delete, and add processing to the same information stored in the database via a network. By organizing requests, always provide correct information to users in real time.

For example, as shown in FIG. 6, when a user 64 operates the terminal 62 to refer to the information A stored in the database 61, a user 65 operates the terminal 63 to operate the database 61. When a correction such as writing is performed on the information A stored in the database 61, it is necessary to notify the user 64 of the correction result of the information A stored in the database 61 in real time.

For this reason, the consistency of the information stored in the database 61 is maintained by performing exclusive control or the like that gives the right to modify the information A stored in the database 61 to only a single user in real time. Was like that.

[0007] As shown in FIG.
3 stores a large amount of data 74, converts the database 73 into a computer system, and converts the structure of the abstracted complicated information 72 into an appropriate data model 75 in order to sufficiently respond to the request of the user 71. It was replaced with a physical file on the computer.

[0008] The system operator 76 performs maintenance work on a large amount of data 74 stored in the database 73 while maintaining the consistency of the complicated data model 75.

Further, as shown in FIG. 8, a system developer 83 develops a database system based on an abstraction model 81 and a request 82 of a user or an operator.
He proposed an appropriate data model and a computer model.

In this case, in order to provide the user with correct data in real time, an exclusive control method of the database is devised for each process, or a state change notification method of the database is devised. In addition, in order to be able to operate the database efficiently, we devised a maintenance method for each data table of the database,
And devised ways to maintain consistency between data tables.

Hereinafter, a conventional database system will be described with reference to the drawings. In FIG. 9, when a request to access the database 41 is implemented on a computer, the table to be accessed and the processing unit are divided into units called transactions 43, and the processes 43, 4
As work units on a computer called 6, 47,
The processing is executed by allocating system resources such as the main storage device 44 and the auxiliary storage device 45 on the computer.

[0012] These processes 42, 46, 47 are generally occupied solely by system resources, and their independence is kept very high. for that reason,
The communication between the processes 42, 46 and 47 and the allocation of system resources are managed by the operating system 48.

For example, in an operating system such as UNIX or OS / 2, which can process a plurality of processes in parallel, a multi-process compatible operating system uses messages and pipes for inter-process communication and kernel resources such as semaphores for exclusive control of system resources. providing.

In a database system, UNI
When a program structure such as X or OS / 2 is used as it is, and an access request to the database 41 issued for each of the processes 42, 46, and 47 is made, the processes 42, 46 using kernel resources such as semaphores are used. , 47 are controlled exclusively.

Thus, even when many users access the same information in the database 41 via the network and contention of access requests occurs, it is possible to control such that different requests do not occur at the same time. And

For example, the same information A on the database 41
If the process 47 changes the information A in the processes 46 and 47 accessing the
Need to be notified to process 47 of the change.

The process 46 needs to re-read the information A, redraw the screen information, and perform a conditional branch in the access processing based on the status change notification. This is performed by using an inter-process communication function such as a message or a pipe provided by the system 48.

That is, when the process 47 changes the information A, the status change notification of the database 41 is sent to the process 46 using a message, and the process 46 re-reads the information A, so that each process 42, 46 and 47 can always refer to real-time information.

When replacing the complex information model, which has been abstracted in the database 41, with a physical file of a computer, the data model is subdivided into data table groups of tabular images, and as shown in FIG. By using a relational database in which a data item having a unique value for each record, that is, a key item, and associating a data table with the key item of the relational database, a complicated information model can be created. I try to make it happen.

That is, in the data model constructed by the relational database, for example, when the information of the main table 51 is deleted, the information of the dependent tables 53 and 54 associated with the information of the main table 51 is also deleted. , Ensuring database consistency. Further, when a key item is changed in the main table 51, all key information of the dependent tables 53 and 54 associated with the information of the main table 51 is also changed.

The communication function between the processes 42, 46 and 47 and the processing function for ensuring the consistency of the database are implemented for each of the processes 42, 46 and 47.

[0022]

However, in the conventional database system, exclusive control of the database 41 is performed by each process 4 using a semaphore of a kernel resource or the like.
If the resource cannot be acquired, the process 42, 46, 47 itself is temporarily stopped, and the function of the retry process for reacquiring the resource is also performed in each process. 42, 46, and 47 were implemented.

For this reason, the system developer assigns the exclusive control function and the retry processing function to the processes 42, 46 and 47.
There is a problem that it takes time to write and test a program to be implemented every time.

Each process 4 is notified of a status change of the database 41 by using a message of a kernel resource or the like.
2, 46, and 47, and each process 42, 4
A function for transmitting and receiving communication between the processes 42, 46, and 47 is implemented for each of the processes 42, 46, and 47.
Processes 42 and 4 to which the message is transmitted every 6 and 47
6, 47 were managed.

For this reason, the system developer has a problem that it takes time to write and test a program for implementing the message transmission / reception function for each of the processes 42, 46, and 47.

Furthermore, in order to ensure the consistency of the database 41, it is necessary to reflect changes to the main tables 51 and 52 in the dependent tables 53 and 54. In the case of a complicated information model, the data tables created in the relational database There is a problem that the number increases and the burden on the system developer increases.

It is an object of the present invention to provide an access method and an access apparatus for a database system capable of easily creating a program for exclusive control of a database, notification of a state change, and consistency maintenance.

[0028]

According to the present invention, a database class using an object-oriented programming language is created, and as its static member data, for example, exclusive information, status, and the like. Exclusive control, state change notification, and consistency control are performed by providing change information and consistency information and referencing these static member data from individual database instances.

As a result, it is not necessary to code a program for performing exclusive control, state change notification, and consistency control for each process, thereby reducing man-hours.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An access device of a database system according to one embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a functional configuration of an access device according to an embodiment of the present invention.

In FIG. 1, a database class storage unit 1 stores a database class that holds kernel resources and process information as static member data. The static member data includes exclusive information 2, state change information 3, consistency information 4, and the like.

The database control means 2 refers to the static member data stored in the database class storage means 1 from the database instance to control the database such as exclusive control 6, status change notification 7, and consistency control 8. Do.

As described above, according to the access device of the database system according to the embodiment of the present invention, the kernel resources and the process information are replaced with the static member data and the access program is replaced with the method by object orientation. To define the database class. The system is constructed using a class that owns the substance of the database class, that is, the instance linkage method.

Thus, information such as semaphores and messages, which are kernel resources, and process information including a user interface such as a screen can be linked to a database access program, and a process developer can design a program for each process. Need not be performed, and an increase in man-hours due to the complexity of the data model can be avoided.

Next, a database access method according to an embodiment of the present invention will be described with reference to the drawings. In the database access method according to an embodiment of the present invention, the object-oriented programming language S
Although malltalk, AT & TC ++ and the like are used, in the following description, the case where AT & TC ++ is used is taken as an example.

In C ++, as shown in FIG. 2, unique static member data that can be referenced from the instances 14 of all the database classes 12 is declared using the static keyword 11. In the data area 13 of the static member data, information for exclusive control, a database name, an identifier of a process in which the instance 14 was generated,
Stores a chain indicating the relationship between the dependent data tables.

Thus, when an access message is sent from the program to the instance 14, exclusive control processing and consistency maintenance processing can be performed by referring to the data area 13.

FIG. 3 is a diagram showing control information indicating the data structure of a data table according to one embodiment of the present invention. In FIG. 3, a control information section 22 is provided at the head of the physical file of the data table 21. The control information section 22 stores a data item name, a data type, a data length, and the like. The data item name of the parent data table to be stored is also stored.

Next, a description will be given of a description method of the data area 13 according to one embodiment of the present invention with reference to the drawings.
In FIG. 4, when a database instance is declared in a process, a database open process is performed in a constructor that is a constructor of the database instance. When the database instance is completed normally, a database name and a process identifier are registered in a data area 13. Do. Further, a chain indicating the relationship of the dependent data tables 21 is obtained from the control information section 22 of the data table 21 of the opened database, and the chains are independently registered in the data area 13.

Here, the database name is the data area 13
If the information has already been registered, it indicates that the database has already been opened by another process of the application, and the database name and the process identifier, which are the main information, are added to the linear list.

When information is deleted from the data area 13, when the database instance in the process goes out of the scope, the data area is deleted based on the database name and the process identifier in the destructor which is the annihilator. Search for 13.

By sending a message to the instance 14, information can be explicitly deleted from the data area 13 even within the scope. Next, an exclusive control method according to an embodiment of the present invention will be described.

In FIG. 2, when an access message such as reference, deletion, update, or addition of a database is transmitted to the instance 14, the instance 14 searches the data area 13 based on the database name and refers to the process identifier. To check what lock condition is issued to the same database by a process other than the process to which it belongs.

For example, if a record lock has been issued from another process, this is notified to the caller of the own process, and if retry is set there, during the retry time, Stops its own process and tries to gain access again.

As described above, exclusive control can be performed by referring to the database class 12, so that
As in the related art, there is no need for a system developer to write a program for performing exclusive control and verify the operation, thereby reducing man-hours and simplifying work.

As described above, according to the exclusion control method according to the embodiment of the present invention, a message is sent to the instance 14 of the database class 12 using the access method, thereby accessing the database in the process. Can be. At this time, the access method can determine whether to perform exclusive control by referring to the exclusive information, which is static member data of the database class 12.

As a result, the exclusive control is hidden in the database class 12, so that it is not necessary to describe the exclusive control in the process, and the design and test work of the system developer can be reduced.

Next, a state change notification method according to an embodiment of the present invention will be described. In FIG. 2, when the access message is transmitted to the instance 14 and the description information of the database is changed, the instance 14 refers to the data area 13 on the basis of the database name, thereby identifying a process identifier other than the process identifier to which the instance 14 belongs. The search is performed, and the instance 14 of the process identified by the process identifier is notified that the database has been changed.

The instance 14 that has received the notification that the database has been changed rereads the description information of its own database or redraws the screen. If the access method is being executed, it is used as information for determining a conditional branch.

As described above, the status change notification can be performed by referring to the database class 12, so that the system developer describes a program for performing the status change notification for each process as in the related art, and executes the operation. This eliminates the need for verification, and can reduce man-hours and simplify work.

As described above, according to the state change notification method according to one embodiment of the present invention, a plurality of processes own the same database instance 14, and one of the processes changes to the database instance 14. Is added to the state change information, which is the static member data of the database class 12, with its instance 14
Is changed, the instance 14 of another process, which is a copy thereof, can also know from the static member data that a state change has occurred,
For example, it is possible to make a branch determination of reloading / redrawing screen / processing.

As a result, the state change is hidden in the database class 12, so that it is not necessary to describe the state change notification in the process, and the design and test work of the system developer can be reduced.

Next, a method for maintaining consistency according to an embodiment of the present invention will be described. In FIG. 2, the message for changing the description information of the database is the instance 14
Is transmitted to the instance 14, the instance 14 follows the chain that is the static member data, checks the dependency of the data table 21, and changes the description information of the dependent data table 21 if necessary.

Then, when all the information in the data table 21 is completed, the self description information is changed. When making these changes, exclusive control is performed, and after the change of the description information is completed, each process is notified of the latest description information.

As described above, by referring to the database class 12, maintenance of the consistency of the database can be performed. Therefore, as in the related art, the consistency of the database can be maintained while paying attention to the dependencies of the database. This eliminates the need to write a program for performing maintenance and verify the operation, thereby reducing man-hours and simplifying work.

As described above, according to the consistency maintenance method according to an embodiment of the present invention, when a process gives a message to a database instance 14 to delete or change a record, that instance 14 By referring to the dependent table by tracing the relational database association information described in the static member data of the database class 12, it is determined whether or not the delete message given to the instance 14 is permitted, and the change message is reflected in the dependent table. It can be performed.

As a result, the maintenance of the consistency is also hidden in the database class 12, so that it is not necessary to describe the process for maintaining the consistency in the process.
The load on the design and test work of the system developer can be reduced.

[0058]

As described above, according to the present invention,
Exclusive information, data such as database information used for each process, and the access program are defined as classes using the object-oriented programming method, so that programs that perform exclusive control, state change notification, and consistency control are defined. There is no need to code for each process, and a library that reduces man-hours can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a functional configuration of an access device of a database system according to one embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a database class according to an embodiment of the present invention.

FIG. 3 is a diagram showing a schematic configuration of a data table according to one embodiment of the present invention.

FIG. 4 is a diagram illustrating a registration method for a data area according to an embodiment of the present invention.

FIG. 5 is a diagram showing a schematic configuration of a conventional database system.

FIG. 6 is a diagram showing the operation of a conventional database system.

FIG. 7 is a diagram showing a conventional database system operation method.

FIG. 8 is a diagram showing a conventional database system development method.

FIG. 9 is a block diagram showing a schematic configuration of a conventional database system.

FIG. 10 is a diagram showing a dependency relationship of a data table in a conventional relational database.

[Explanation of symbols]

 1 Database class storage means 2 Exclusive information 3 State change information 4 Consistency information 5 Database control means 6 Exclusive control 7 State change notification 8 Consistency control 11 Static keyword 12 Database class 13 Data area 14 Instance 21 Data table 22 Control information section

Claims (8)

[Claims] 1. A method for accessing a database system for storing a data structure of a data table for storing data as a table in a table format in a partial area of a physical file of the database, comprising the steps of: Database access management information is stored in a static member data portion of the class library, and a database instance accesses the database by referring to the access management information. how to access. 2. A class library of a database is created using an object-oriented programming language, and access management information describing a database name and a process identifier is stored in a static member data section of the class library. An exclusive control method of a database system, wherein exclusive control of a database is performed by referring to the database. 3. A database class library is created using an object-oriented programming language, access management information describing a database name and a process identifier is stored in a static member data section of the class library, and the database is updated. Thereafter, a state change notification of the database system is performed by referring to the access management information. 4. A class library of a database is created using an object-oriented programming language, and access management information describing a dependency relationship for each data item is stored in a static member data section of the class library; A method for maintaining the consistency of a database system, comprising maintaining the consistency of a database by updating a data table of the database with reference to the database. 5. A database class storing means for storing a database class having static member data as kernel resources and process information, and a database control for controlling a database by referring to said static member data from a database instance. Means for accessing a database system. 6. The access device according to claim 5, wherein exclusive information is stored as the static member data, and exclusive control of the database is performed with reference to the exclusive information. 7. The access device according to claim 5, wherein status change information is stored as the static member data, and a status change notification of a database is issued with reference to the status change information. 8. The access apparatus according to claim 5, wherein consistency information is stored as the static member data, and consistency control of a database is performed with reference to the consistency information.