Data Independence

Data Independence

Capacity to change the schema at one level of a database system without having to change the schema at the next higher level.

Logical Data Independence: The capacity to change the conceptual schema without having to change the external schemas and their application programs.

Physical Data Independence: The capacity to change the internal schema without having to change the conceptual schema.

Data independence is accomplished because, when the schema is changed at some level, the schema at the next higher level remains unchanged; only the mapping between the two levels is changed.

However, the two levels of mappings create an overhead during compilation or execution of a query or program, leading to inefficiencies in the DBMS.