Distributed database ( English distributed database, DDB ) - a database , the components of which are located in various nodes of a computer network in accordance with any criterion.
Content
General information
A distributed database, sometimes called a distributed / parallel database or in the English abbreviation , DDB is precisely a single database, and not an arbitrary set of files individually stored on different network nodes and which is a distributed file system. Data is DDB only if it is connected in accordance with some structural formalism, relational model , and access to it is provided by a single high-level interface .
Distributed databases can have a different level of replication - from the complete lack of duplication of information to the complete duplication of all information in all distributed copies (for example, blockchain ).
Transparency Technology
The distribution (including fragmentation and replication ) of a database across multiple nodes is invisible to users. This property is called transparency , and the technology of distributing and replicating data across multiple computers connected by a network is fundamental to implementing the concept of data independence from the storage medium. This is ensured by several types of transparency:
- network transparency, and therefore distribution transparency
- replication transparency
- fragmentation transparency
- access transparency, which means that users deal with a single logical database image and access distributed data in the same way as if it were stored centrally.
Ideally, complete transparency implies the presence of a query language for a distributed DBMS, not different from the language for a centralized DBMS.
See also
- Cloud Databases
- Distributed computing
Literature
- C. J. Data Introduction to Database Systems = An Introduction to Database Systems. - 7th ed. - "Williams", 2001. - ISBN 5-8459-0138-3 .
- M. Tamer Ozzu, P. Valduriz Distributed and parallel database systems // Database Management Systems, No. 04, 1996.