"The ability to change the Schema at one level of database system without having to change the Schema at the next higher level is called data independence". Data Independence is divided into two categories:
1) Logical Data Independence: It is the ability to change conceptual schema without making any changes to application programs or external schema. In Logical data Independence new rows and columns are added without changing user views and programs.it is more difficult to achieve rather than Physical Data Independence.
2) Physical Independence: It is the ability to change internal schema without making any changes to conceptual schema.Hence there is no need to change the external schema.Physical data independence hides all details of storage structure from user applications. Modifications at physical level improves performance and any new change is absorbed by the mapping techniques.
1) Logical Data Independence: It is the ability to change conceptual schema without making any changes to application programs or external schema. In Logical data Independence new rows and columns are added without changing user views and programs.it is more difficult to achieve rather than Physical Data Independence.
2) Physical Independence: It is the ability to change internal schema without making any changes to conceptual schema.Hence there is no need to change the external schema.Physical data independence hides all details of storage structure from user applications. Modifications at physical level improves performance and any new change is absorbed by the mapping techniques.
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