kel080388
Posts : 14
Join date : 2009-06-30
Age : 35
Location : Cabanatuan
 | | Subject: Database Management System 3rd July 2009, 22:23 | |
| A DBMS is a set of software programs that controls the organization, storage, management, and retrieval of data in a database. DBMS are categorized according to their data structures or types. It is a set of prewritten programs that are used to store, update and retrieve a Database. The DBMS accepts requests for data from the application program and instructs the operating system to transfer the appropriate data. When a DBMS is used, information systems can be changed much more easily as the organization's information requirements change. New categories of data can be added to the database without disruption to the existing system.
Organizations may use one kind of DBMS for daily transaction processing and then move the detail onto another computer that uses another DBMS better suited for random inquiries and analysis. Overall systems design decisions are performed by data administrators and systems analysts. Detailed database design is performed by database administrators.
Database servers are computers that hold the actual databases and run only the DBMS and related software. Database servers are usually multiprocessor computers, with generous memory and RAID disk arrays used for stable storage. Connected to one or more servers via a high-speed channel, hardware database accelerators are also used in large volume transaction processing environments. DBMSs are found at the heart of most database applications. Sometimes DBMSs are built around a private multitasking kernel with built-in networking support although nowadays these functions are left to the operating system.
DBMS MODELS
- The hierarchical model: The data is sorted hierarchically, using a downward tree. This model uses pointers to navigate between stored data. It was the first DBMS model.
- The network model: like the hierarchical model, this model uses pointers toward stored data. However, it does not necessarily use a downward tree structure.
- The relational model (RDBMS, Relational database management system): The data is stored in two-dimensional tables (rows and columns). The data is manipulated based on the relational theory of mathematics.
- The deductive model: Data is represented as a table, but is manipulated using predicate calculus.
- The object model (ODBMS, object-oriented database management system): the data is stored in the form of objects, which are structures called classes that display the data within. The fields are instances of these classes
By the late 1990s, relational databases were the most commonly used (comprising about three-quarters of all databases).
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trasher
Jr-Captain
Posts : 18
Join date : 2009-06-30
Age : 36
| | Subject: Re: Database Management System 4th July 2009, 11:36 | |
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