Data Independence in DBMS : Physical & Logical With Examples

Data Independence -


-> Data independence can be explained using the three-schema architecture.


-> Data independence is ability to modify a schema definition in one level without affecting a schema definition in the next higher level.


There are 2 types of data independence in DBMS:-


1. Physical data Independence:-   

-> Physical data independence can be defined as the capacity to change the internal schema without having to change the conceptual schema.

-> 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.



Examples of changes under Physical Data Independence

1. Modifying the file organization technique in the Database
2. Switching to different data structures.
3. Changing the access method.

4. Modifying indexes.




2. Logical data Independence:-

-> Logical Data Independence is the ability to change the conceptual scheme without changing:

1. External views
2. External API or programs

Any change made will be absorbed by the mapping between external and conceptual levels.

-> When compared to Physical Data independence, it is challenging to achieve logical data independence.

Examples of changes under Logical Data Independence

1. Merging two records into one

2. Breaking an existing record into two or more records