Lesson 4: An Intrduction to Database Management Systems

A database is a collection of related files that are usually integrated, linked or cross-referenced to one another. The advantage of a database is that data and records contained in different files can be easily organized and retrieved using specialized database management software called a database management system (DBMS) or database manager.

After reading this lesson, you should be able to:

DBMS Fundamentals

A database management system is a set of software programs that allows users to create, edit and update data in database files, and store and retrieve data from those database files. Data in a database can be added, deleted, changed, sorted or searched all using a DBMS. If you were an employee in a large organization, the information about you would likely be stored in different files that are linked together. One file about you would pertain to your skills and abilities, another file to your income tax status, another to your home and office address and telephone number, and another to your annual performance ratings. By cross-referencing these files, someone could change a person's address in one file and it would automatically be reflected in all the other files. DBMSs are commonly used to manage:

DBMSs and File Management Systems

Computerized file management systems (sometimes called file managers) are not considered true database management systems because files cannot be easily linked to each other. However, they can serve as useful data management functions by providing a system for storing information in files. For example, a file management system might be used to store a mailing list or a personal address book. When files need to be linked, a relational database should be created using database application software such as Oracle, Microsoft Access, IBM DB2, or FileMaker Pro.

The Advantages of a DBMS

Improved availability: One of the principle advantages of a DBMS is that the same information can be made available to different users.

Minimized redundancy: The data in a DBMS is more concise because, as a general rule, the information in it appears just once. This reduces data redundancy, or in other words, the need to repeat the same data over and over again. Minimizing redundancy can therefore significantly reduce the cost of storing information on hard drives and other storage devices. In contrast, data fields are commonly repeated in multiple files when a file management system is used.

Accuracy: Accurate, consistent, and up-to-date data is a sign of data integrity. DBMSs foster data integrity because updates and changes to the data only have to be made in one place. The chances of making a mistake are higher if you are required to change the same data in several different places than if you only have to make the change in one place.

Program and file consistency: Using a database management system, file formats and system programs are standardized. This makes the data files easier to maintain because the same rules and guidelines apply across all types of data. The level of consistency across files and programs also makes it easier to manage data when multiple programmers are involved.

User-friendly: Data is easier to access and manipulate with a DBMS than without it. In most cases, DBMSs also reduce the reliance of individual users on computer specialists to meet their data needs.

Improved security: As stated earlier, DBMSs allow multiple users to access the same data resources. This capability is generally viewed as a benefit, but there are potential risks for the organization. Some sources of information should be protected or secured and only viewed by select individuals. Through the use of passwords, database management systems can be used to restrict data access to only those who should see it.

The Disadvantages of a DBMS

There are basically two major downsides to using DBMSs. One of these is cost, and the other the threat to data security.

Cost: Implementing a DBMS system can be expensive and time-consuming, especially in large organizations. Training requirements alone can be quite costly.

Security: Even with safeguards in place, it may be possible for some unauthorized users to access the database. In general, database access is an all or nothing proposition. Once an unauthorized user gets into the database, they have access to all the files, not just a few. Depending on the nature of the data involved, these breaches in security can also pose a threat to individual privacy. Steps should also be taken to regularly make backup copies of the database files and store them because of the possibility of fires and earthquakes that might destroy the system.

Knowledge Check

What is an advantage of major database management systems?
  1. The same information can be made available to different users.
  2. Fires and earthquakes that might destroy the system.
  3. Once an unauthorized user gets into the database, they have access to all the files.
  4. Time and cost to implement.
Answer A is correct. An advantage of major database management systems are that the same information can be made available to different users.
Answer B is incorrect. Please try again.
Answer C is incorrect. Please try again.
Answer D is incorrect. Please try again.

Lesson Wrap-Up

In this lesson, a database management system is defined, as well as its purposes and functions. One of the most powerful aspects of a DBMS is the ability to organize and retrieve data from different, but related, files. However, using databases and DBMSs has its advantages and disadvantages. As you proceed with your career, you should be aware of the tradeoffs that accompany using these computerized tools. The tradeoffs we have discussed so far include such things as the redundancy, accuracy, accessibility, and user-friendliness of data in a DBMS. Being educated about the strengths and weaknesses of DBMSs will allow you to make more effective decisions about how to organize and use data.

Now that you have completed this lesson, you should be able to: