Architecture of database System | Introduction to Database management system

DATABASE SYSTEM ARCHITECTURE

Three layers of architecture of DBMS:-

1. External level/View level

2. Conceptual level/Logical level

3. Internal level/Physical level

1. External level/View level-It is the user view and it shows the data that is relevant to the user. It deals with the way in which individual user view the data.It hides the details of internal and conceptual level.

2. Conceptual level/Logical level-It describes what data is stored in the database and the relationship among them.It contains the logical structure of the database as seen by the DBA.

3. Internal level/Physical level- It is the physical representation of the database. It covers the data structures used to store the data on storage devices,It also deals with storage space allocation.

                                  (3-LEVEL ARCHITECTURE)

OBJECTIVES OF 3 LEVEL ARCHITECTURE-

1. Each user access the same data but have a different view.

2. No dealing with physical storage details.

3. DBA changes database storage structure without effecting users view.

4. The main objective of this 3 level architecture is to provide DATA INDEPENDENCE.