Data Independence

Data Independence:

A major objective for three-level architecture is to provide data independence. Data independence refers characteristic of being able to modify the schema at one level of the database system without affecting the schema at the next higher level. It saves time and cost required when the database is modified or altered.

Types of Data independence

The data independence is classified as two types and they are as below:

· Logical Data Independence:

Logical data independence indicates that the conceptual schema can be changed without affecting the existing external schema. Logical data independence is used to separate the external level from the conceptual view. The user view of the data would not be affected by any changes to the conceptual view of the data. These changes may include insertion or deletion of attributes, altering table structures entities or relationships to the logical schema etc. The change would be absorbed by the mapping between the external and conceptual levels. Logical data independence also insulates application programs from operations such as combining two records into one or splitting an existing record into two or more records.

· Physical Data Independence:

Physical data independence can be defined as the capacity to change the internal schema without having to change the conceptual schema. Modifications at the internal levels are occasionally necessary to improve performance. If we do any changes in the storage size of the database system server, then the Conceptual structure of the database will not be affected. Physical data independence is used to separate conceptual levels from the internal levels. The change would be absorbed by the mapping between the conceptual and internal levels.

x

Advantages of Data independence

1.      Ability of improving performance

2.      Alterations in data structure does not requires alterations in application programs

3.      Implementation details can be hidden from the users

4.      Reduction of incongruity

5.      Tractability in improvement of system

6.      Affordable prices of maintaining system

7.      Providing the best services to the users

8.      Permit users to focus on general structure

9.      Enforcement of standards

10.   Improvement of security

1    11.  The state of being undamaged or undivided can be improved

-profshardulp.patil@gmail.com