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Reduced Redundancy


In case of a file-system, same data getting stored in different locations for different applications leads to data redundancy

In contrast, a DBMS removes much of this redundancy. That is one reason why a DBMS is sometimes referred to as a nonredundant collection of data items.

In reality, a DBMS sometimes has some measure of redundancy, to imporove access times or to simplify addressing methods or to increase the capability to recover from an accidental loss of data..

Because of the trade-off between nonredundancy and other desirable criteria, a DBMS is said to have controlled or Minimal redundancy or it is said that a DBMS removes harmful redundancy.

As an example, consider the example mentioned in centralized control page. In this case, increase in the number of employees in the enterprise, increases redundancy i.e., many copies of emp-num and emp-name data exist, leading to wastage of storage space.

The disadvantages of uncontrolled redundancy are
- extra cost of storing multiple copies of the same data item
- multiple updating operations and costly deletions
- data at different locations being in different stages of updation

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