We discussed earlier some of the limitations of applications that rely on traditional file management. What are the advantages of the database approach?
- Eliminating data redundancy.With the database approach to data management, data need only be stored once. Applications that need data can access the data from the central database. For example, in Figure 3.5, part (a), there are multiple versions of the inventory master data, while in part (b) of that figure there is but one. Further, Figure 3.6 depicts the same data elements on more than one file, whereas Figure 3.7 shows each data element only once. An organization using the applications-based file approach to data management must incur the costs and risks of storing and maintaining these duplicate files and data elements.
- Ease of maintenance. Because each data element is stored only once, any additions, deletions, or changes to the database are accomplished easily. Contrast this to the illustration in Figure 3.6, where a change in a salesperson, territory, or customer combination, for instance, would require a change in three different files.
- Reduced storage costs. By eliminating redundant data, storage space is reduced, resulting in associated cost savings. However, in most database installations, this savings is more than offset by the additional costs of DBMS software.
- Data integrity.This advantage, like several others, results from eliminating data redundancy. As mentioned earlier, storing multiple versions of the same data element is bound to produce inconsistencies among the versions. For instance, the salesperson and sales territory data might differ among their many versions, not only because of clerical errors but because of timing differences in making data maintenance changes. We could make similar comments about inconsistent data resulting from the timing differences that might occur during event data processingof the inventory master data by the sales and inventory applications. With only one version of each data element stored in the database, such inconsistencies disappear.
- Data independence. As illustrated in part (b) of Figure 3.5, the database approach allows multiple application programs to use the data concurrently. In addition, the data can be accessed in several different ways (e.g., through applications processing, online query, and report writing programs). And, the access can be quickly changed by modifying the definition of the tables or views. With the traditional applications-based file approach, the programs would have to be revised to provide access to more or less data.
- Privacy.The security modules available through DBMS software can contain powerful features to protect the database against unauthorized disclosure, alteration, or destruction. Control over data access can typically be exercised down to the data element level. Users can be granted access to data for reading or updating (add, revise, delete) data. Other ways to implement security include data classification(i.e., data objects are given classification levels and users are assigned clearance levels) and data encryption (discussed in Chapter 9).
What are the relative advantages of the database approach?
These advantages add greatly to the incentive for firms relying on legacy systems to move to database-supported applications.