What Is Data Independence in DBMS ?

The ability to modify a schema definition in one level without affecting a schema definition in the next level is called data independence.
There are two levels of data independence.

1. Physical Data Independence.
2. Logical Data Independence.

1. Physical Data Independence :

It is the  ability to modify the physical schema without causing application programs to be rewritten.

2. Logical Data Independence :

It is the ability to modify the logical schema without causing application program to be rewritten.

Logical data independence is more difficult than is the physical data independence.