Data Independence Types
Data independence has two types. They are:
- Physical Independence
- Logical Independence.
Data independence can be explained as follows: Each higher level of the data architecture is immune to changes of the next lower level of the architecture.
Physical Independence: The logical scheme stays unchanged even though the storage space or type of some data is changed for reasons of optimisation or reorganisation. In this external schema does not change. In this internal schema changes may be required due to some physical schema were reorganized here. Physical data independence is present in most databases and file environment in which hardware storage of encoding, exact location of data on disk,merging of records, so on this are hidden from user.
Logical Independence: The external scheme may stay unchanged for most changes of the logical scheme. This is especially desirable as the application software does not need to be modified or newly translated.
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