A Database Management System (DBMS) is a software program that typically operates on a database server or mainframe system to manage structured data, accept queries from users, and respond to those queries. A typical DBMS has the following features (Stair and Reynolds, 2004):
Provides a way to structure data as records, tables, or objects
Accepts data input from operators and stores that data for later retrieval
Provides query languages for searching, sorting, reporting, and other "decision support" activities that help users correlate and make sense of collected data
Provides multi-user access to data, along with security features that prevent some users from viewing and/or changing certain types of information
Provides data integrity features that prevent more than one user from accessing and changing the same information simultaneously
Provides a data dictionary (metadata) that describes the structure of the database, related files, and record information
Most databases are operational databases, meaning that data going into the database is used in real time to support the ongoing activities of a business. A point-of-sale business accounting system is an example. As items are sold, the inventory database is updated and the inventory information is made available to the sales staff. The invoicing, order entry, and related systems are also updated (Stair and Reynolds, 2004). Most DBMS systems are client/server based and operate over networks. The DBMS is an engine that typically runs on a powerful server or cluster of servers, in a storage area network (SAN) environment or mainframe with a high-performance channel to a large data store. The DBMS accepts requests from clients that may require sorting and extracting data. Once the server has processed the request, it returns the information to the client.
DATABASE ARCHITECTURE
The original PC networks were based on file sharing architectures, where the