Saturday 15 June 2019

Component and Interfaces of DBMS

A database management system involves five major components: data, hardware,software, procedure, and users. These components and the interface between the components are shown in below figure 

Component and Interfaces of DBMS
1. Hardware

Hardware consists of a set of physical electronic devices such as computers (together with associated I/O devices like disk drives), storage devices, I/O channels, electromechanical devices that make interface between computers and the real world systems etc, and so on.

2. Software

The software includes the DBMS software, application programs together with the operating systems including the network software if the DBMS is being used over a network.

3. Data

Data in the database are raw facts. Useful information is retrieved from these raw facts. The main features of the data in the database are listed later:
  1. The data in the database is well organized (structured)
  2. The data in the database is related
  3. The data are accessible in different orders without great difficulty

The data in the database is persistent, integrated, structured, and shared

4. Procedures

Procedures refer to the instructions and rules that help to design the database and to use the DBMS. The users that operate and manage the DBMS require documented procedures on how use or run the database management system. These may include.
  1. Procedure to install the new DBMS.
  2. To log on to the DBMS.
  3. To use the DBMS or application program.
  4. To make backup copies of database.
  5. To change the structure of database.
  6. To generate the reports of data retrieved from database.
5. People Interacting with Database

Here people refers to the people who manages the database, database administrator, people who design the application program, database designer and the people who interacts with the database, database users. A DBMS is typically run as a back-end server in a local or global network, offering services to clients directly or to Application Servers.

Peoples interacting with Database

5.1 Application Programmers

The people who write application programs in programming languages (such as Visual Basic, Java, or C++) to interact with databases are called Application Programmer.
5.2 Database Administrators 
A person who is responsible for managing the overall database management system is called database administrator or simply DBA.
5.3 End-Users
The end-users are the people who interact with database management system to perform different operations on database such as retrieving, updating, inserting, deleting data etc.

5.4 Database Designer

Database designer can be either logical database designer or physical database designer. 

  • Logical database designer is concerned with identifying the data, the relationships between the data, and the constraints on the data that is to be stored in the database.
  • The physical database designer takes the logical data model and decides the way in which it can be physically implemented.

5.5 Database Manager

Database manager is a program module which provides the interface between the low level data stored in the database and the application programs and queries submitted to the system.

6. Data Dictionary

A data dictionary, also known as a “system catalog,” is a centralized store of information about the database. It contains information about the tables, the fields the tables contain, data types, primary keys, indexes, the joins which have been established between those tables, referential integrity, cascades update, cascade delete, etc. This information stored in the data dictionary is called the “Metadata.”


The information (data) about the data in a database is called Metadata

7. Functional Components of Database System Structure

The functional components of database system structure are:
  1. Storage manager.
  2. Query processor.
1. Storage Manager

Storage manager is responsible for storing, retrieving, and updating data in the database. Storage manager components are:
  1. Authorization and integrity manager.
  2. Transaction manager.
  3. File manager.
  4. Buffer manager.

Authorization and Integrity Manager

Checks the integrity constraints and authority of users to access data.

Transaction Management

Transaction-management component ensures that the database remains in a consistent state despite system failures and transaction failure.

File Manager

File manager manages the allocation of space on disk storage. The file manager can:

– Create a file
– Delete a file
– Update the record in the file
– Retrieve a record from a file

Buffer Manager

Buffer manager is responsible for fetching data from disk storage into main memory.

2. Query processor:

The query processor transforms user queries into a series of low level instructions. It is used to interpret the online user's query and convert it into an efficient series of operations in a form capable of being sent to the run time data manager for execution. The query processor uses the data dictionary to find the structure of the relevant portion of the database and uses this information in modifying the query and preparing and optimal plan to access the database.

Check video explanation from below link


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