Definition :- Data independence is allows the database to structure changed. It means data can be add, deleted or data attributes altered with disruption to a existing system.
Two level of data independence are:
- Logical data independence :- Insulates application program from logical operations such as combining two records into one or splitting an existing record into two or more records.
- Physical data independence :- indicates that the physical storing structures or devices used for storing data could be change without needing a change in the records structure or application program.
Logical data independence
- Logical data is concerned with a structure of data.
- Logical data is very difficult as the retrieving of data is dependent on the logical structure of data.
- Application program need not be changed if new field is added or deleted from the database.
Physical data independence
- Physical data is concerned with storage of data.
- Physical data is easy to retrieve.
- It is concerned with the change of the storage device.