A distributed database is a database in which data is stored across different physical locations. It may be stored in multiple
computers located in the same physical location (e.g. a data centre); or maybe dispersed over a
network of interconnected computers. Unlike
parallel systems
Parallel is a geometric term of location which may refer to:
Computing
* Parallel algorithm
* Parallel computing
* Parallel metaheuristic
* Parallel (software), a UNIX utility for running programs in parallel
* Parallel Sysplex, a cluster of IB ...
, in which the processors are tightly coupled and constitute a single database system, a distributed database system consists of loosely coupled sites that share no physical components.
System administrators can distribute collections of data (e.g. in a database) across multiple physical locations. A distributed database can reside on organised
network servers or
decentralised independent computers on the
Internet
The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a ''internetworking, network of networks'' that consists ...
, on corporate
intranets
An intranet is a computer network for sharing information, easier communication, collaboration tools, operational systems, and other computing services within an organization, usually to the exclusion of access by outsiders. The term is used in c ...
or
extranets, or on other organisation
networks. Because distributed databases store data across multiple computers, distributed databases may improve performance at
end-user worksites by allowing transactions to be processed on many machines, instead of being limited to one.
[
O'Brien, J. & Marakas, G.M.(2008) Management Information Systems (pp. 185-189). New York, NY: McGraw-Hill Irwin]
Two processes ensure that the distributed databases remain up-to-date and current:
replication
Replication may refer to:
Science
* Replication (scientific method), one of the main principles of the scientific method, a.k.a. reproducibility
** Replication (statistics), the repetition of a test or complete experiment
** Replication crisi ...
and
duplication.
# Replication involves using specialized software that looks for changes in the distributive database. Once the changes have been identified, the replication process makes all the databases look the same. The replication process can be complex and time-consuming, depending on the size and number of the distributed databases. This process can also require much time and computer resources.
# Duplication, on the other hand, has less complexity. It identifies one database as a
master and then duplicates that database. The duplication process is normally done at a set time after hours. This is to ensure that each distributed location has the same data. In the duplication process, users may change only the master database. This ensures that local data will not be overwritten.
Both replication and duplication can keep the data current in all distributive locations.
[
Besides distributed database replication and fragmentation, there are many other distributed database design technologies. For example, local autonomy, synchronous, and asynchronous distributed database technologies. The implementation of these technologies can and do depend on the needs of the business and the sensitivity/ confidentiality of the data stored in the database and the price the business is willing to spend on ensuring data security, consistency and integrity.
When discussing access to distributed databases, Microsoft favors the term distributed query, which it defines in protocol-specific manner as " y SELECT, INSERT, UPDATE, or DELETE statement that references tables and rowsets from one or more external OLE DB data sources".
]Oracle
An oracle is a person or agency considered to provide wise and insightful counsel or prophetic predictions, most notably including precognition of the future, inspired by deities. As such, it is a form of divination.
Description
The word '' ...
provides a more language-centric view in which distributed queries and distributed transactions form part of distributed SQL.[
]
See also
* Centralized database
* Data grid
* Distributed cache
* Distributed data store
* Distributed hash table
* Routing protocol
References
*M. T. Özsu and P. Valduriez, ''Principles of Distributed Databases'' (3rd edition) (2011), Springer,
*Elmasri and Navathe, ''Fundamentals of database systems'' (3rd edition), Addison-Wesley Longman,
*''Oracle Database Administrator's Guide 10g'' (Release 1), http://docs.oracle.com/cd/B14117_01/server.101/b10739/ds_concepts.htm
{{Databases
Data management
Types of databases
Distributed computing architecture
Applications of distributed computing
Database management systems