TRADITIONAL FILE PROCESSING SYSTEMS
When computer-based data processing was first available, there were no databases. To
be useful for business applications, computers had to store, manipulate, and retrieve
large files of data. Computer file processing systems were developed for this purpose.
Although these systems have evolved over time, their basic structure and purpose have
changed little over several decades.
As business applications became more complex, it became evident that traditional
file processing systems had a number of shortcomings and limitations (described next).
As a result, these systems have been replaced by database processing systems in most
business applications today. Nevertheless, you should have at least some familiarity
with file processing systems since understanding the problems and limitations inherent
in file processing systems can help you avoid these same problems when designing
database systems.
File Processing Systems at Pine Valley Furniture Company
Early computer applications at Pine Valley Furniture (during the 1980s) used the traditional
file processing approach. This approach to information systems design met
the data processing needs of individual departments rather than the overall information
needs of the organization. The information systems group typically responded to
users’ requests for new systems by developing (or acquiring) new computer programs
for individual applications such as inventory control, accounts receivable, or
human resource management. No overall map, plan, or model guided application
growth.
Three of the computer applications based on the file processing approach are shown
in Figure 1-2. The systems illustrated are Order Filling, Invoicing, and Payroll. The figure
also shows the major data files associated with each application. A file is a collection of related
records. For example, the Order Filling System has three files: Customer Master,
Inventory Master, and Back Order. Notice that there is duplication of some of the files
used by the three applications, which is typical of file processing system.
When computer-based data processing was first available, there were no databases. To
be useful for business applications, computers had to store, manipulate, and retrieve
large files of data. Computer file processing systems were developed for this purpose.
Although these systems have evolved over time, their basic structure and purpose have
changed little over several decades.
As business applications became more complex, it became evident that traditional
file processing systems had a number of shortcomings and limitations (described next).
As a result, these systems have been replaced by database processing systems in most
business applications today. Nevertheless, you should have at least some familiarity
with file processing systems since understanding the problems and limitations inherent
in file processing systems can help you avoid these same problems when designing
database systems.
File Processing Systems at Pine Valley Furniture Company
Early computer applications at Pine Valley Furniture (during the 1980s) used the traditional
file processing approach. This approach to information systems design met
the data processing needs of individual departments rather than the overall information
needs of the organization. The information systems group typically responded to
users’ requests for new systems by developing (or acquiring) new computer programs
for individual applications such as inventory control, accounts receivable, or
human resource management. No overall map, plan, or model guided application
growth.
Three of the computer applications based on the file processing approach are shown
in Figure 1-2. The systems illustrated are Order Filling, Invoicing, and Payroll. The figure
also shows the major data files associated with each application. A file is a collection of related
records. For example, the Order Filling System has three files: Customer Master,
Inventory Master, and Back Order. Notice that there is duplication of some of the files
used by the three applications, which is typical of file processing system.
DUPLICATION OF DATA
Because applications are often developed independently in file processing systems, unplanned duplicate data files are the rule rather than the exception.
For example, in Figure 1-2 the Order Filling System contains an Inventory Master
File, whereas the Invoicing System contains an Inventory Pricing File. These files
contain data describing Pine Valley Furniture Company’s products, such as product
description, unit price, and quantity on hand. This duplication is wasteful because it
requires additional storage space and increased effort to keep all files up to date. Data
formats may be inconsistent or data values may not agree (or both). Reliable metadata
are very difficult to establish in file processing systems. For example, the same data
item may have different names in different files, or conversely, the same name may be
used for different data items in different files.
LIMITED DATA SHARING
With the traditional file processing approach, each application has its own private files, and users have little opportunity to share data outside their own applications. Notice in Figure 1-2, for example, that users in the Accounting Department have access to the Invoicing System and its files, but they probably do not have access to the Order Filling System or to the Payroll System and their files.
Managers often find that a requested report requires a major programming effort
because data must be drawn from several incompatible files in separate systems. When
different organizational units own these different files, additional management barriers
must be overcome.
LENGTHY DEVELOPMENT TIMES
With traditional file processing systems, each new application requires that the developer essentially start from scratch by designing new file formats and descriptions and then writing the file access logic for each new program.
The lengthy development times required are inconsistent with today’s fast-paced business environment, in which time to market (or time to production for an information
system) is a key business success factor.
EXCESSIVE PROGRAM MAINTENANCE
The preceding factors all combined to create a heavy program maintenance load in organizations that relied on traditional file processing systems. In fact, as much as 80 percent of the total information system’s development budget might be devoted to program maintenance in such organizations.
This in turn means that resources (time, people, and money) are not being spent on
developing new applications.
It is important to note that many of the disadvantages of file processing we have mentioned can also be limitations of databases if an organization does not properly apply the database approach. For example, if an organization develops many separately managed databases (say, one for each division or business function) with little or no coordination of the metadata, then uncontrolled data duplication, limited data sharing, lengthy development time, and excessive program maintenance can occur. Thus, the database approach, which is explained in the next section, is as much a way to manage organizational data as it is a set of technologies for defining, creating, maintaining, and using these data.