Data Independence in DBMS

 Data Independence

Introduction-

The ability to modify a schema definition in one label without affecting a schema. Definition in the next higher level is called Data Independence.

Data independence is one of the main advantage of  DBMS. 

Advantage of Data Independence-

• Integrity can be maintained
• Security can be imposed
• Concurrent access can be achieved
• Better recovery mechanism
• IS's conflicting requirements can be balanced .

Disadvantage of Data Independence-

• Complexity, seem to require more work (Skills, time, resources)
• Eventually it pays off
• Higher impact of failure.
• Possibly, reduced local performance.

Types of Data Independence-

1. Physical data independence
2. Logical data independence

 

     1.Physical Data Independence-

The separation of the conceptual view from the internal view enables us to provide a logical description of the database without the need of satisfy physical structures. This is often called physical data independence. 

Modification at the physical level is occasionally necessary in order to improve performance. Simply, it refers to the immunity of an application to change in the internal mode and the excess strategy. 

Examples of physical independence are reorganization of files adding in new excess path etc.

    2. Logical Data Independence-

The separation of the external views from the conceptual views, which enables the user to change the conceptual view without affecting the external views or application program, is called logical data independence. Simply, it referred to the immunity of the external model to change it in the conceptual model.

  Example of logical data independence are addition/removal of entities.

Difference between Physical Data Independence and Logical Data Independence:

Logical Data Independence-

Logical data independence is the ability to modify the conceptual schema without making it necessary to rewrite application programs. Such a modification might be adding a field to a record and application program views, hides this change from the program.

Physical Data Independence-

Physical data independence is the ability to modify the physical schema without making it necessary to rewrite application programs. Such modification include changing from the unblock to blocked record storage on from sequential to random access files.

Conclusion-

These were some of the point discussed in the post-  Data Independence and types of  Data Independence

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