Free Essay About Database Management Systems

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Database Replication

Database replication is the copying a dataset across different server and making it available for all users. Database replication is done for boosting the performance and also for fault tolerance. Replication is a strategy for maintaining distributed databases which are efficient and consistent, allowing users to access databases independently (Wiesmann, Pedone, Schiper, Kemme & Alonso, 2000). There are three different types of database replication strategies namely:

Snapshot Replication: This is the simplest strategy that involves copying data from one server to another.

Transactional Replication: In this replication strategy a primary copy of the database from the main server is received which is followed by a series of periodic and timely updates.
Merging Replication: Database replication is performed by combining data from different servers into a single database server (Wiesmann, Pedone, Schiper, Kemme & Alonso, 2000).

Distributed Queries

Distributed databases allow to decentralize data that is available for users across diverse geographical locations. Distributed queries provide an ability to retrieve data from different database sites in a network and present the results for processing. Distributed queries retrieve data from dissimilar heterogeneous sources of data. Distributed queries are powerful as they can be executed in parallel with a decentralized database system. The intermediate results of the distributed queries can also be obtained in parallel and sent to the computer systems that require those results. The implementation of a distributed query for data retrieval relies on the underlying algorithm for the query optimization. Executing the distributed queries on a single dedicated system is an important aspect of achieving optimal performance in minimum execution time (Apers, Hevner, & Yao, 1983).

MS SQL Server

Microsoft SQL Server is one of the earliest database management systems that was developed by the company Microsoft. It is a relational database software that allows to store, retrieve and manipulate data through various operations. The original variant of SQL Server launched by Microsoft was in the year of 1989 after which a series of enhanced version of the DBMS were release. The most stable one of them was launched in 1995 called SQL Server 6.0. After SQL Server, 6.0, the next stable, and popular version was SQL Server 2000 in the year of 2000. Microsoft has been releasing an upgraded version of SQL Server on a regular basis. In 2010, Microsoft launched Azure SQL, which was a cloud-based database. The latest version of SQL Server is 2014 which has most of the capabilities of database management, distributed computing and cloud support through Windows Azure (Nielsen & Parui, 2011).

Replication in SQL Server

SQL Server allows replication by copying and maintaining a database across distributed databases in a network. SQL Server enables both transactional and merges replication.
A scenario of merge replication is exchange of data in consumer POS (Point of Sale) systems. Another example is data warehouse reporting where data from multiple sites is integrated to publish a report (Msdn.microsoft.com, 2015).

Distributed Queries in SQL Server

Microsoft SQL Server backs distributed queries to access data from multiple data sources or database instances by using an OLE DB provider. The distributed queries are in the form of transactional SQL statements referencing the external data sources directly.
A scenario for is generating a report for a large insurance company by accessing data from different data sources in SQL Server, MS Excel, Oracle and MS Access by using distributed queries in SQL Server for each data source. (Technet.microsoft.com. 2015).

References

Wiesmann, M., Pedone, F., Schiper, A., Kemme, B., & Alonso, G. (2000). Database replication
techniques: A three parameter classification. In Reliable Distributed Systems, 2000.
SRDS-2000. Proceedings The 19th IEEE Symposium on (pp. 206-215). IEEE.
Apers, P. M. G., Hevner, A. R., & Yao, S. B. (1983). Optimization algorithms for distributed
queries. Software Engineering, IEEE Transactions on, (1), 57-68.
Nielsen, P., & Parui, U. (2011). Microsoft SQL server 2008 bible (Vol. 607).
John Wiley & Sons.
Msdn.microsoft.com. (2015). SQL Server Replication. Retrieved 23 March 2015, from
https://msdn.microsoft.com/en-us/library/ms151198.aspx
Technet.microsoft.com. (2015). Distributed Queries. Retrieved 23 March 2015,