Database Applications and Kinds of Database Systems

Since a database is a model of an organization, the processing of the database should correspond to the processing of the organization. Except for very small organizations, business activity is divided into functions. The record club, for example, includes these functional areas:

Member Service

Order Processing

Purchasing

Collections

Each of the business functions has its own information requirements. Member Service needs information about members and orders. Order Processing needs information about members, orders, and inventory. Purchasing needs information about orders and inventory. Collections needs information about members and their accounts. Observe that no functional area needs all of the data. Different portions are used by different functional areas. Also note that some of the data is shared by two or more functional areas. Member data, for example, is needed by Member Service, Order Processing, and Collections. In a file processing system, each functional area would probably maintain its own file of Member records, resulting in terrible data duplication problems. Also, it is likely that all copies of the MEMBER file would not be maintained precisely the same way, and so the data would likely soon disagree, causing other problems. In a database system, all the areas share the same centralized data. It is precisely because centralized data can serve many functional areas that databases are so popular. A database application is a business computer system that processes a portion of a database in order to meet the information needs of a business group, department, or functional area. In a sense, an application provides a window into the database for a particular user group. For now, think of an application as a collection of computer screens, printed reports, and transaction processing programs that access the part of a database needed to solve problems for a user group. Database processing systems are usually very large; after all, they support the needs of many diverse user groups. Therefore, we divide database processing into separate applications. First, recall that a business is usually divided into separate functional areas. Thus, the computer screens, reports, and transaction processing programs for the Order Processing area are probably different from the computer screens, reports, and transaction processing programs for the Collections area. When we develop applications, we incorporate the interfaces (screens and reports) needed by one group into a cohesive package. Thus, for example, order entry clerks would see a computer screen format that was meaningful to them, while collections agents would see the style of computer screen they could best read and understand. Second, database data is one of an organization's most valuable assets. It is undesirable to allow every user to access every portion of the database. Loan processing clerks in a bank, for example, should not be permitted to change savings account balances. Breaking database processing into applications provides improved control over access to the data. Finally, it is easier and less risky for developers to build applications one by one than to try to build them all at once. Dividing processing into applications limits the scope of development to a series of smaller projects as opposed to one large project.

Kinds of Database Systems

Database systems are made up of five components: hardware, DBMS software and application programs, the database itself, procedures, and people. One way to classify database systems is according to the number of users and the number of applications they support. This classification will affect each of the five components of the system. For example, in a single-user database system, only one user at a time processes the database. In contrast, multi-user database systems are processed concurrently by many users. The hardware in a multi-user system is much more extensive than that of a single-user system. Similarly, when databases are processed concurrently, special precautions need to be taken to prevent one user's processing from interfering with another's. Thus, the DBMS software and user procedures for a single-user system are different from those of a multi-user one. Database systems can also support one or many applications. Combining these two dimensions, there are four basic types of database systems. Single-user, single-application databases are most frequently found on microcomputers. Multi-user, single-application databases are found on microcomputers connected via local area networks (LANs) and also on minicomputers. Multi-user, single-application databases often are used by software vendors who develop packages for specific uses called vertical markets. Such a vendor might incorporate a database into a general ledger accounting package, for example. If so, the database generated would serve only that particular application. Single-user, multi-application database systems are generally found on microcomputers. Finally, multi-user, multi-application databases are generally found in larger companies on mainframe computers. Database systems can migrate from one category to another. For example, a single-user, single-application database system can be extended to support multiple users. Even more commonly, a second application can be added to a single-application database system. During such migrations, developers try to implement the second application without negatively impacting the first one. For example, sometimes the presence of a second application will degrade the performance of the first.

Imran Zafar writes articles about computer basics and database management such as free computer dictionary, Linux operating system.