03 Sep  Admin

This architecture has three levels:

1. External level  :-

    External level is also called view level. The reason this level is called “view” is because several users can view their desired data from this level which is internally fetched from database with the help of conceptual and internal level mapping. External level is the “ top level ” of the Level of DBMS Architecture.

Facts about External level:

  1. An external level is only related to the data which is viewed by specific end users.
  2. This level includes some external schemas.
  3. External schema level is nearest to the user
  4. The external schema describes the segment of the database which is needed for a certain user group and hides the remaining details from the database from the specific user group

2. Conceptual level  :-

      Conceptual level is also called logical level .The whole design of the database such as relationship among data, schema of data etc. are described in this level. It is maintained by DBA.

Facts about Conceptual level:

  1. Defines all database entities, their attributes, and their relationships
  2. Security and integrity information
  3. In the conceptual level, the data available to a user must be contained in or derivable from the physical level

3. Internal level  :-

       Internal level is also known as physical level. This level describes how the data is actually stored in the storage devices. It is responsible for storage allocation. This is the lowest level of the architecture.

Facts about Internal level:

  1. The internal schema is the lowest level of data abstraction
  2. It helps you to keeps information about the actual representation of the entire database. Like the actual storage of the data on the disk in the form of records
  3. The internal view tells us what data is stored in the database and how
  4. It never deals with the physical devices. Instead, internal schema views a physical device as a collection of physical pages.