Characteristics of distributed database, distributed DBMS characteristics, basic requirements of a distributed dbms, DDBMS characteristics
Characteristics of Distributed Database Management System (DDBMS)
A DDBMS has the following
characteristics in common;
- It handles a collection of logically related shared data.
- In distributed database, each site has some data that are same or similar like other sites data. These data can be accessed by any request initiated at any server that is part of the application. Hence, they are shared.
- The data are normally split into fragments.
- The data of an entity set is usually divided into many fragments (horizontal, vertical, hybrid) based on the application that accesses the data. This is done based on several factors.
- The data fragments may also be replicated (duplicated).
- Some of the data fragments may be duplicated and maintained in several sites. That is, the data available at site A may also be made available at site B.
- The sites are linked by communication network.
- A distributed database is a database that is spread over multiple sites and linked through communication networks.
- The data at each site is controlled by the local DBMS.
- The site on which the data stored is the owner of the data. And, this data is handled by the DBMS software installed in that site.
- The local requests must be handled by local DBMS autonomously.
- As said above, the local DBMS can answer autonomously the queries that are requesting the data stored in that site only. There is no need to consult with other sites.
- DBMS at each site must participate in at least one global application.
- The applications that are accessing the data in a distributed database may access local data as well as global data. If the DBMS is accessing the global data, we would say that as the distributed database. Hence, we need all of our sites to participate in at least one global data access.
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