DBMS-Three Level Architecture

Three level architecture is also called three schema architecture

what are we going to learn ?

1. Reason of creation of 3 level architecture.
2. What is 3 level /schema architecture.

Why is 3 level architecture created ?

Three level architecture was created to keep the physical database separate from the user applications.

Three Level Architecture

What is 3 level architecture ?

This architecture has three levels:

1. External level
2. Conceptual level
3. Internal level

1.External level

• It is also known as view level.
• This is highest level architecture and closest to the user.
• The user doesn’t need to know the database schema details such as data structure, table definition etc.
• External level is related to the data which is viewed by individual end users.

2. Conceptual level

• It is also known as logical level.
• The conceptual level is a higher level than the physical level.
• This level is maintained by DBA(database administrator).
• The whole design of the database such as relationship among data ,schema of data etc.are described in this level.
• It is the middle level between external or internal levels.

3. Internal level

• It is also known as physical level.
• This is the lowest level of the architecture.
• This data is stored in the external hard drives in the form of bits.
• This level describes how the data actually stored in the storage device.
• This physical level also discuess encryption techniques.
• This level is also responsible for allocating space of the data.