Database Reference
In-Depth Information
17. Future plans. What plans has the vendor made for the future of the system? This information is
often difficult to obtain, but you can get an idea by looking at the performance of the vendor
with respect to how it has kept the existing system up to date. How easy has it been for users to
convert to new versions of the system?
18. Other considerations. This is a final catch-all category that contains any special requirements
not covered in the other categories. For many organizations, existing financial and other applica-
tion software and existing hardware limit the DBMS choice.
After the DBA examines each DBMS with respect to all the preceding categories, the DBA and manage-
ment can compare the results. Unfortunately, this process can be difficult because of the number of categories
and their generally subjective nature. To make the process more objective, the DBA can assign a numerical
ranking to each DBMS in each category (for example, a number between 0 and 10, where 0 is poor and 10 is
excellent). Furthermore, the DBA can assign weights to the categories. Weighting allows an organization to
signify which categories are more critical than others. Then, you multiply each number used in the numerical
ranking by the appropriate weight and add the results, producing a weighted total. Finally, you compare the
weighted totals for each DBMS, producing the final evaluation.
How does the DBA arrive at the numbers to assign each DBMS in the various categories? Several methods
are used. The DBA can request feedback from other organizations that are currently using the DBMS being
considered. The DBA can read journal reviews of the various DBMSs. Sometimes the DBA can obtain a trial
version of the DBMS, and members of the staff can give it a hands-on test. In practice, the DBA usually com-
bines all three methods. Whichever method is used, however, the DBA must carefully create the checklist and
determine weights before starting the evaluation; otherwise, the findings may be inadvertently slanted in a
particular direction.
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DBMS Maintenance
After the organization selects and purchases the DBMS, the DBA has primary responsibility for it. The DBA
installs the DBMS in a way that is suitable for the organization. If the DBMS configuration needs to be
changed, it is the DBA who makes the changes.
When the vendor releases a new version of the DBMS, the DBA reviews it and determines whether the
organization should upgrade to it. If the decision is made to convert to the new version or perhaps to a new
DBMS, the DBA coordinates the conversion. The DBA also handles any fixes to problems in the DBMS that
the vendor releases.
When a problem occurs that affects the database, the DBA coordinates the people required to resolve the
problem. Some people, such as programmers and users, are from inside the organization, and others, such as
hardware and software vendors, are from outside the organization.
When users have special one-time processing needs or extensive query requirements against the data-
base, the DBA coordinates the users so that their needs are satisfied without unduly affecting other users.
Data Dictionary Management
The DBA also manages the data dictionary. Essentially, the data dictionary is the catalog mentioned in
Chapter 7, but it often contains a wider range of information, including information about tables, fields,
indexes, programs, and users.
The DBA establishes naming conventions for tables, fields, indexes, and so on. The DBA creates the data
definitions for all tables, as well as for any data integrity rules and user views. The DBA also updates the
contents of the data dictionary. Finally, the DBA creates and distributes appropriate reports from the data
dictionary to users, programmers, and other people in the organization.
Training
The DBA provides training in the use of the DBMS and in how to access the database. The DBA also coordi-
nates the training of users and the technical staff responsible for developing and maintaining database appli-
cations. In those cases where the vendor of the DBMS provides training, the DBA handles the scheduling to
make sure users receive the training they require. Training is a big expense, but successful organizations
make the investment to ensure that their employees are knowledgeable and productive in handling the criti-
cal data resource.
