22-05-2012, 10:28 AM
DBMS - Database Management Systems
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Companies need to process a large amount of data. Manual storage of this data wastes a lot of time while retrieving it. It also requires tedious clerical hours to arrange the data in the form required by top management. Storing this data in a way to facilitate easy access is very important and that is why computers are used in organizations. This is possible using DBMS. DBMS, besides allowing you to store large amounts of data, allows you to retrieve information easily whenever and in whichever format it is desired.
RDBMS - Relational Database Management Systems
The functionality of RDBMS is the same as DBMS except that the features offered for data storage and retrieval are very advanced. These systems are based on mathematical SET theory. A RDBMS ensures that the data stored in the database is accurate and relevant. Excellent security features are offered by these systems. RDBMS packages are used in medium to large-scale organizations, especially, those where data has to be made available on distributed networks. These systems have capability to store a very large amount of data and have quick data retrieval mechanisms. They also have elaborate database administration for handling multi-users, storage, and failures.
An RDBMS uses SQL (Structures Query Language) to access data from database. This is a A database has to be persistent, meaning that the information stored in a database has to continue to exist even after the application(s) that saved and manipulated the data have ceased to run. A database also has to provide some uniform methods that are not dependent on a specific application for accessing the information that is stored inside the database. This is a pretty liberal definition of a database. Lotus Notes calls its message stores "databases", and by
thisdefinition they qualify. MUMPS calls its associative storage a database, and while it takes a bit of a stretch,even that meets this definition. There are a number of new database technologies that include objectorienteddatabases and associative databases, and they seem to qualify as databases under this definition too. Text or flat binary files don't qualify as databases under this definition, since only the application that createdone of these files knows enough about the file's contents to make use of the information stored within the file.They meet the persistence part of the DBMS definition, but not the independent access part of the definition. Other "standards" like the Berkeley DB format supported by Perl, Python, and related languages do more orless qualify as a DBMS. While it isn't what most people think of when they think about DBMS setups, it doesmeet both the persistence and uniform access conditions for a DBMS. An RDBMS is a Relational Data Base Management System. This adds the additional condition that the system supports a tabular structure for the data, with enforced relationships between the tables. This excludes the databases that I've listed so far since they either don't support a tabular structure at all, or don't enforce relationships between tables.
Microsoft's Jet database engine qualifies as an RDBMS under this definition, even though it seems like the majority of its users ignore the "relational" side of the engine by failing to declare foreign keys.
IndividualFoxPro files do not qualify because they don't have any built-in method for declaring or supporting relationships, even though nearly every FoxPro system I've ever seen expects or relies on these relationships. Most DBAs think of an RDBMS as a client/server system. The database engine runs on a server, and clientapplications connect and request data from the server. Microsoft SQL Server, Oracle, DB2 (both the Z seriesand the UDB product), and most of the other "industrial grade" databases in use today use this mental model.