DBMS Data Independence | Data Independence in DBMS

Data Independence is ability to modify a schema definition in one level without affecting a schema definition in the next higher level.

Data Independence is the property of DBMS that allows the User or Database Administrator to change the database schema at one level without affecting the schema at another level. 

There are two levels of data independence:

1. Physical Data Independence

2. Logical Data Independence

Physical Data Independence: 

Physical Data Independence is the ability to change the physical level without affecting the logical or Conceptual level. Hence, modification in the Physical level should not result in any changes in the Logical or View levels. 

Physical data independence allow us to modify the storage device, file structure, location of the database, etc. without changing the definition of conceptual or view level.

If we do any changes in the storage size of the database system server, then the Conceptual structure of the database will not be affected.

Logical data independence: 

Logical Data Independence is the ability to change the logical level without affecting the external or view level. Hence, modification in the logical level should not result in any changes in the view levels or application programs. 

Logical data independence separates external level from the conceptual level.

The user view of the data would not be affected by any changes to the conceptual level of the data. These changes may include adding new attributes to a relation, deleting existing attributes of the relation, altering table structures etc. 

Figure: Data Independence