Role of Fragmentation in Distributed Database System

Distributed database is a logically interrelated collection of shared data physically distributed over a computer network. Since the database is decompose into numbers of fragments .Fragmentation ?plays an important role in distributed database system .Hence each fragment is stored in one or more computers under the control of a seprate DBMS. There are mainly three type of fragmentation called horizontal, vertical, mixed. Horizontal fragment is a subset of tuples that groups together the tuples in relation that are collectively used by the important transaction. Vertical fragmentation is a subset of attributes. In vertical fragmentation ,the fragments can be stored at the site that need them, In addition ,performance is improved .Mixed fragmentation consist of a horizontal fragment that is subsequently vertically fragmented ,or a vertical fragment that is then horizontally fragmented.