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by Dinesh Thakur Category: Advanced Database Tech.

Data can be stored in different computers by fragmenting the whole database into several pieces called fragments. Each piece is stored at a different site.

Fragments are logical data units stored at various sites in a distributed database system.

Advantages of fragmentation 

Before we discuss fragmentation in detail, we list four reasons for fragmenting a relation

Usage

In general, applications work with views rather than entire relations. Therefore, for data distribution, it seems appropriate to work with subsets of relation as the unit of distribution.

Efficiency

Data is stored close to where it is most frequently used. In addition, data that is ,not needed by' local applications is not stored.

Parallelism

With fragments as the unit of distribution, a transaction can be divided into several sub queries that operate on fragments. This should increase the degree of concurrency, or parallelism, in the system, thereby allowing transactions that can do so safely to execute in parallel.

Security

Data not required by local applications is not stored, and consequently not available to unauthorized users.

Disadvantages of fragmentation

Fragmentation has two primary disadvantages, which we have mentioned previously:

Performance

The performance of global application that requires data from several fragments located at different sites may be slower.

Integrity

Integrity control may be more difficult if data and functional dependencies are fragmented and located at different sites.

 

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About Dinesh Thakur

Dinesh ThakurDinesh Thakur holds an B.SC (Computer Science), MCSE, MCDBA, CCNA, CCNP, A+, SCJP certifications. Dinesh authors the hugely popular blog. Where he writes how-to guides around Computer fundamental , computer software, Computer programming, and web apps. For any type of query or something that you think is missing, please feel free to Contact us.