The Database Management System (DBMS) architecture shows how data in the database is viewed by the users. It is not concerned about how the data are handled and processed by the DBMS.
It helps in implementation, design, and maintenance of a database to store and organize information for companies. The concept of DBMS depends upon its architecture. The architecture can be designed as centralized, decentralized, or hierarchical.
The architecture of DBMS can be defined at three levels as follows −
The main objective of the three level architecture is nothing but to separate each user view of the data from the way the database is physically represented. The database internal structure should be unaffected while changes to the physical aspects of storage.
The DBA should be able to change the conceptual structure of the database without affecting all other users.
External level describes a part of the database that is relevant to each user. This level insulates the users from the details of conceptual and the internal level.
Conceptual level describes what data is stored into the database and the relationship among the data.
It represents the following −
All the entities, attributes and their relationships.
The constraints on the data.
Security and integrity information.
Internal level is the physical representation of the database on the computer. This level describes how the data is stored in the database. It covers the data structure and file organization used to store the data on storage devices.
The levels in the architecture of DBMS are shown below in diagram form −