Distributed database management system
A distributed database management system is a software system that permits the management of a distributed database and makes the distribution transparent to the users. A distributed database is a collection of multiple, logically interrelated databases distributed over a computer network. Sometimes "distributed database system" is used to refer jointly to the distributed database and the distributed DBMS.
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distributed database managemnet system(DDBMS) is specially developed for hetrogeneous database platforms. DDBMS focus mainly on hetrogeneous databse management system (HDBMS). it is a databse for managing databases stored on multiple computers in a network. a distributed database is a set of databses stored on multiple computersthat typically appears to applications on a single database. consequently, an application can simultaneously acess and modify the data in several databses in a network. DDBMS is a software that manages a distributed database while making the distribution transparent to the user. the major aims of DDBMS are:- 1. to carry out transparent management of distributed, fragmented and replicated data. 2.improved reliability/availibility through distributed transaction. 3.improved performance. 4.easier and economical system expansion.
a DDBMS should provide data independence. for this, it should implement network transparency, replication transparency and fragmentation transparency.
various factors that can affect performance of DDBMS:- 1.proximity- data proximity can affect its performance. thus greater the proximity of data to the system from where it is being accessed the faster the system. 2.parallelism- parallelism further demands full data replication(so that data is availaible where it is being executed) and updates so that all the data copies have the same state irrespective of there location. a DDBMS also permits easy expansion of the system which is an advantage over centralized databse.
In DDBMS we propose a hetrogeneous multidatabase system architecture which solves solve some of inherent problems of hetrogenity such as reliability, semantic integrity, and protection. the hetrogeneous multidatabse system environment that has been considered involves a connection of pre-existing databse system, with a possibility of adding new databse system at any time during system lifetime. accesing and managing data from several existing independent databses pose complex problems that can be classifies into platforms, location and semantic levels. this DDBMS describes a methodology and environment intended to address the problem of providing users and programmers with an abstract interface to independent hetrogeneous databases.
References
- M. T. Özsu and P. Valduriez, Principles of Distributed Database Systems (2nd edition), Prentice-Hall, 1999. ISBN 0-13-659707-6.