What are the advantages and disadvantages of a distributed database system?

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May 18, 2014 by Ozgur Ozden

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Before we start listing the advantages and disadvantages of the distributed systems i would like to briefly explain what distributed database system is. A distributed database is a system which consists of two or more database located at the same physical location or distributed over a networks of connected computers such as mainframes, PC’s, tablets, cell phones. Since the database is distributed, different user profiles may access to the different parts of the database without interfering each other.
The distributed database system started to appear when companies and business get larger and operation spread out to different geographical locations. Distributed network may be located on the network servers on Internet, intranets or extranets or on other company networks.
We may list the advantages and disadvantages of this system as below.

ADVANTAGES
DISADVANTAGES
Organizational structure: In these days many business and companies are operating in different parts of the world. So it is an advantage to have database servers located in different parts of the world, custom made and designed for the needs of the local market but connected to the international network of the company. In this systems user can create local queries on the other hand headquarters may create global queries about the situation of the company so there is no bottleneck.
Complex System: Distributed systems are much more complex to setup and difficult to maintain.
Integrity: Integrity of such systems are difficult to maintain because of its various server site nature.
Sharing and freedom: Data located at one geographical location can be shared with another user at another location. Depending on the need of the local business rules database can be customized and local DBA can maintain the system. Global DBA is responsible for the whole system management. So different levels of autonomy can be assigned to users.
Security: Since the system is distributed to many remote locations, new entry points increases security risk. In central systems data can be supervised rather easily compare to the distributed systems. But in distributed systems whole network must be secured as well Thakur (n.d.)
Data maintainability: In centralized systems if database fails all users influenced from the result. But in distributed systems if one node fails this does not influence the user on other nodes. Distributed systems are designed taking these failures into account. This affected node can be re-routed.
Data Format: if different data formats and systems used in different sites, data management might be problematic.
Data Accessibility: Since the same or similar data exists in many different nodes, failure at one node may not affect the others so data is still accessible.
Also any errors made on the local database does not affect the whole organization.
Data can be joined and a new table can be created even data resides on different local sites.
Optimization: Optimization is difficult to apply in such systems because of the variety of the sites.
Static SQL can not be applied to such systems according to moreprocess.com.

Performance: Since the closest data has greater demand access speed and performance is better compared to centralized systems. In addition to this, each node, site deals with the small portion of the overall database, CPU and I/O will be different again compare to centralized systems Thakur (n.d)
Deadlock: Taking care of the deadlocks in distributed systems is more difficult according to moreprocess.com.
Budget: It does require less budget to set up a distributed system rather than one powerful centralized system. It is also very cost effective to add nodes when it is necessary rather than the whole mainframe

Growth: In a distributed growth or expansion can be handled easily. New sites can be added without doing modifications on the other sites Coronel (2011).

Traffic: Traffic on the network can be reduced since the system is divided into different pieces.

References:
1- Thakur (n.d) What are the Advantages and Disadvantages of Distributed Database Management System? (online) Available at: http://ecomputernotes.com/database-system/adv- database/advantages-and-disadvantages-of-ddbms [accessed at: 10.10.2013]
2- Coronel (2011) Database Systems: Design, Implementation, and Management. 9th Edition, Cengage Learning
3- Distributed Database, Chapter 12 (Online) Available at: http://wps.pearsoned.co.uk/wps/media/objects/10977/11240737/Web%20chapters/Chapter%2012_WEB.pdf [accessed at: 10.10.2013]
4- Advantages and disadvantages of distributed database (n.d) (Online) Avaiable at: http://www.moreprocess.com/sql/advantages-and-disadvantages-of-distributed-database [accessed at: 11.10.2013]

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