Database Reference
In-Depth Information
The DBA must periodically monitor the users' activity on the database. DBMS products
include features that collect and report statistics. For example, some of these reports may
indicate which users have been active, which files—and perhaps which data items—have
been used, and which access methods have been employed. Error rates and types also can be
captured and reported. The DBA analyzes these data to determine whether a change to the
database design is needed to improve performance or to ease the users' tasks. If change is nec-
essary, the DBA will ensure that it is accomplished.
The DBA should analyze run-time statistics on database activity and performance.
When a performance problem is identified (by either a report or a user's complaint), the DBA
must determine whether a modification of the database structure or system is appropriate.
Examples of possible structural modifications are establishing new keys, purging data, deleting
keys, and establishing new relationships among objects.
When the vendor of the DBMS being used announces new product features, the DBA
must consider them in light of the overall needs of the user community. If the DBA decides to
incorporate the new DBMS features, the developers must be notified and trained in their use.
Accordingly, the DBA must manage and control changes in the DBMS as well as in the data-
base structure.
Other changes in the system for which the DBA is responsible vary widely, depending on
the DBMS product as well as on other software and hardware in use. For example, changes in
other software (such as the operating system or the Web server) may mean that some DBMS
features, functions, or parameters must be changed. The DBA must therefore also tune the
DBMS product with other software in use.
The DBMS options (such as transaction isolation levels) are initially chosen when little is
known about how the system will perform in the particular user environment. Consequently,
operational experience and performance analysis over a period of time may reveal that
changes are necessary. Even if the performance seems acceptable, the DBA may want to alter
the options and observe the effect on performance. This process is referred to as
tuning,
or
optimizing,
the system. Figure 9-20 summarizes the DBA's responsibilities for managing the
DBMS product.
Maintaining the Data Repository
Consider a large and active Internet database application, such as those used by e-commerce
companies—for instance, an application that is used by a company that sells clothing over the
Internet. Such a system may involve data from several different databases, dozens of different
Web pages, and hundreds, or even thousands, of users.
Suppose that the company using this application decides to expand its product line to
include the sale of sporting goods. Senior management of this company might ask the DBA to
develop an estimate of the time and other resources required to modify the database applica-
tion to support this new product line.
To respond to this request, the DBA needs accurate metadata about the database,
about the database applications and application components, about the users and their
rights and privileges, and about other system elements. The database does carry some
Figure 9-20
Summary of the DBa's
responsibilities for
Managing the DBMS
• Generate database application performance
reports
• Investigate user performance complaints
• Assess need for changes in database structure
or application design
• Modify database structure
• Evaluate and implement new DBMS features
• Tune the DBMS
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