Three schema architecture in DBMS

Dbms three schema architecture

Performance of database management system also depends on the dbms architecture. Generally a three schema architecture in DBMS is used for database design. Database management system software is designed and developed by keep in mind the three different level of schema in dbms. This three schema architecture is basically used to describe the structure of a specific  database system.

Three schema architecture helps in separating the user and physical database. All these three schema are also known as three level which are as shown in  diagram and described below.
dbms three schema architecture

Physical Level

The lowest level in the 3 tier architecture of dbms is physical level, which is also known as the internal level. This physical level describes how data is stored actually in the database
The data is stored in the external hard drives in the form of bits and bytes in this level. This lowest level also responsible for compression and encryption techniques of data.
Physical level indirectly used to describe complex level data structure in detail.

Conceptual Level

The conceptual level is also known as the logical level. It is at a higher level than the physical level. This higher level specifies the relationships between various data tables and describes how the database looks to the users conceptually. 
The conceptual level does not have any relation with  how the data in the database is actually stored.This level tell about what data is actually stored in the database.Conceptual level describe the structure of whole database.
In conceptual level internal detail such as implementation of data is hidden. Generally programmer and administrator work at this level.

External Level

The highest level in the 3 tier architecture of dbms is the external level and closest to the user. It is also called as the view level. This schema also contains sub schema. Each sub schema  describe each view of the database.
This external level shows only the relevant data to the users in the form of views and hides the remaining data. So all individual user can see the data as a different view as per their requirements.
Thus external level of three schema architecture in dbms describes database part that a user or particular group of user is interested in and hide remaining database from that user or group of user.

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