Accounting Information Systems: The Processes and Controls, 2nd Edition

DATABASES (STUDY OBJECTIVE 4)

A database is a collection of data stored on the computer in a form that allows the data to be easily accessed, retrieved, manipulated, and stored. The term “database” usually implies a shared database within the organization. Rather than each computer application having its own file, a database implies a single set of data that is shared by each application that uses the data. Exhibit 13-3 illustrates this data sharing concept.

The top half of the exhibit shows the traditional file-oriented approach to data storage. Each application owns the data file that it uses, and there is no sharing of data even though these applications do in fact use some of the same type of data (such as inventory part numbers and descriptions). This lack of sharing leads to data redundancy. Data redundancy occurs when the same data are stored in more than one file. In this case, inventory part numbers and descriptions may exist in all three files. Data redundancy causes concurrency problems. Concurrency means that all of the multiple instances of the same data are exactly alike. If the same records are stored in many different locations, it is difficult to make sure that they all are updated at the same time (concurrently). For example, changing the address of a customer may mean changing it in three different places. In such cases of data redundancy, errors in updating the data are much more likely to occur. Thus, the data are more likely to have errors. Due to this data ...