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Question number: 789

» Database » MySQL

Essay Question▾

Describe in Detail

What is Data Independence?

Explanation

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

  • There are two levels of data independence:

    • Physical Data Independence

    • Logical Data Independence

    These are described below:

  • Physical Data Independence:

    • Physical Data Independence is the ability to modify the physical schema without requiring any change in application programs.

    • Modifications at the internal levels are occasionally necessary to improve performance. possible modifications at internal levels are change in file structures, compression techniques, hashing algorithms, storage devices, etc.

    • Physical data independence separates conceptual levels from the internal levels.

    • This allows to provide a logical description of the database without the need to specify physical structures.

    • Comparatively, it is easy to achieve physical data independence.

  • Logical Data Independence:

    • Logical data independence is ability to modify the conceptual schema without requiring any change in application programs.

    • Modification at the logical levels are necessary whenever the logical structures of the database is altered.

    • Logical data independence separates external level from the conceptual view.

    • Comparatively it is difficult to achieve logical data independence.

    • Application programs are heavily dependent on logical structures of the data they access. so any change in logical structure also requires programs to change.