Data independence is a characteristic of a database management system (DBMS) that allows changes to be made to the database schema or organization without affecting the applications that use the data. It is a type of data transparency that is important for a centralized DBMS. Data independence helps to keep data separated from all programs that make use of it, and allows stored data to be used for computing and presentation. There are two types of data independence:

• Physical data independence: This refers to the ability to modify the physical structure of the data without affecting the logical or conceptual level. Physical changes include using a new storage device, changing the data structure, or altering indexes to speed up data retrieval.

• Logical data independence: This refers to the ability to modify the logical schema without causing application programs to be rewritten. Modifications at the logical level are necessary whenever the logical structure of the database is altered, for example, when new accounts are added to a banking system.

There are two levels of data independence: first level and second level. The first level is physical data independence, while the second level is logical data independence. The data independence and operation independence together give the feature of data abstraction. Data independence provides the database in a simple structure based on application domain entities to provide the functional requirement, and provides an abstraction of system functional requirements.