Data Independence

Data Independence: The separation of data structure of database from application program that is used to access data from database is called Data Independence. In DBMS, the database and application program are separated from each other. The DBMS sit in between them. You can easily change the structure of database without modifying the application program in an efficient and well manner.

On the other hand in computerized file based system the structure of data items are built into the individual application program of the same file. Thus the data is dependent on the data file and vice versa for data independence of the same file.

There are two kinds of data independence.

  1. Logical data independence
  2. Physical data independence

Logical Data Independence

Logical data independence is the capacity to change the conceptual schema without having to change external schemas or application programs in the data file of the organization. Changes in the conceptual schema may include addition or removal of entities, attributes or relationships or tables and should be possible without having to change existing external view or having to rewrite application programs in the data file of organization.

Physical Data Independence

Physical data independence is the capacity to change the internal schema without having to change the conceptual schema or application programs. Changes in the internal schema may include

  • Using new storage devices.
  • Using different data structures.
  • Switching from one access method to another.
  • Using different file organization or storage structures.
  • Modifying Indexes

The above mentioned changes should be possible without having to change the conceptual or external schema.