Explain Data Independence
Answer:-
Data independence can be defined as the capacity to change the schema at one level of a database
system without having to change the schema at the next higher level. We can define two types of
data independence:
- Logical data independence is the capacity to change the conceptual schema without having to change external schemas or application programs. We may change the conceptual schema to expand the database, to change constraints, or to reduce the database. Only the view definition and the mappings need to be changed in a DBMS that supports logical data independence.
- Physical data independence is the capacity to change the internal schema without having to change the conceptual schema. Hence, the external schemas need not be changed as well. Changes to the internal schema may be needed because some physical files were reorganized for example, by creating additional access structures to improve the performance of retrieval or update.
Data independence occurs 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.