What is tier-3 architecture in DBMS ?

 

This architecture divides the entire system into a three inter related and independent modules.

Physical Level:

  • In data, information about the location of database objects in the data store is kept in this level.
  • Various DBMS users are unaware of the object locations.
  • Information of data storage in secondary devices like disc, tapes  are provided in the level.

Conceptual Level:

  • In this level data is represented in the form of database tables.
  • Example student database contain STUDENT and COURSE Table which is visible to users but they don`t  know where data is stored.
  • In this level, data is referred as logical schema, which describes the kind of data stored in the database.

External Level:

  • Data in terms of conceptual level tables can be specified in this level.
  • To cater the particular needs of user external level view is used.
  • For Example, university FACULTY is interested in looking course details of students and STUDENTS are interested in looking at all details related to academics, accounts, courses and hostel details as well.
  • Different user generates different views. So the main focus of external level is data abstraction.

Three Tier Architecture

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