Types of Fragmentation in Distributed Database


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.

Types of Fragmentation:

Fragmentation can be of following three types:

    i. Horizontal Fragmentation

    ii. Vertical Fragmentation

    iii. Mixed Fragmentation

Horizontal Fragmentation:

In horizontal fragmentation, the relations (tables) are divided horizontally. That is some of the tuples of the relation are placed in one computer and the rest are placed on other computers.

A horizontal fragment is a subject of the total tuples in that relation. The tuples that belong to horizontal fragments are specified by a condition on one or more attributes of the relation.

Vertical Fragmentation:

In vertical fragmentation, some of the columns (attributes) are stored in one computer and the rest are stored in other computers. This is because each site may not need all the attributes of a relation. A vertical fragment keeps only certain attributes of the relation.

Mixed Fragmentation:

Mixed fragmentation is also known as Hybrid Fragmentation. It intermixes horizontal and vertical fragmentation.