Data Independence in DBMS and its Types

When a DBMS needs to expands as per the requirement of users and an organization, it is necessary to update schema's. The ability of changing a schema without affecting other schema is known as data independence. In data independence, a schema is unaffected by changing another schema.

Two levels of data independence are

• Physical Independence
• Logical Independence

Physical Independence

• In physical independence, internal schema is modified without affecting conceptual schema and external schema.
• Physical independence is required for improving performance, by changing storage path of database.
• It is easy as compared to logical independence.
• Physical independence is concerned with internal schema.
• Example, DBA changes storage devices without affecting conceptual and external schema.

Logical Independence

• In logical independence, conceptual schema is modified without affecting external schema (user’s view).
• Logical independence changes structure of a database.
• Logical independence is hard to achieve as compared to physical independence.
• Logical independence is concerned with conceptual schema.
• Example, DBA changes table format of database, changing the format of table does not affect internal and external schema.