Database Reference
In-Depth Information
15. Security is the prevention of unauthorized access, either intentional or accidental, to a database.
17. Authentication refers to techniques for identifying the person who is attempting to access the
DBMS. Three types of authentication are passwords, biometrics, and database passwords. A pass-
word is a string of characters assigned by the DBA to a user that the user must enter to access to
the database. Biometrics identify users by physical characteristics such as fingerprints, voice-
prints, handwritten signatures, and facial characteristics. A database password is a string of char-
acters assigned by the DBA to a database that users must enter before they can access the
database.
19. Permissions specify what kind of access a user has to objects in a database. A workgroup is a
group of users, and a DBA usually assigns appropriate permissions to workgroups.
21. Privacy refers to the right of individuals to have certain information about them kept confidential.
Privacy and security are related because it is only through appropriate security measures that
privacy can be ensured.
23. Data independence is a property that lets you change a database structure without requiring you
to change the programs that access the database.
25. Some utility services that a DBMS should provide include: services that let you change the data-
base structure; services that let you add new indexes and delete indexes that are no longer
needed; facilities that let you use the services available from your operating system; services that
let you export data to and import data from other software products; services that provide support
for easy-to-use edit and query capabilities, screen generators, report generators, and so on;
support for both procedural and nonprocedural languages; and support for an easy-to-use
menu-driven or switchboard-driven interface that allows users to tap into the power of the DBMS
without having to resort to a complicated set of commands.
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CHAPTER 8
DATABASE ADMINISTRATION
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1. The DBA is the database administrator, or the person responsible for the database. The DBA is
necessary because his responsibilities are critical to success in a database environment, especially
when the database is shared among many users.
3. After the DBA determines the access privileges for each user, the DBA creates security policies
and procedures, obtains management approval of the policies and procedures, and then distri-
butes them to authorized users. The DBA uses the DBMS
s security features, such as encryption,
authentication, authorizations, and views, and also uses special security programs, if necessary.
Finally, the DBA monitors database usage to detect potential security violations and takes correc-
tive action if a violation occurs.
5. Certain data, although no longer needed in the production database, must be kept for future refer-
ence. A data archive is a place for storing this type of data. The use of data archives lets an organiza-
tion keep data indefinitely, without causing the database to become unnecessarily large. Data can be
removed from the database and placed in the data archive, instead of just being deleted.
7. A shared lock permits other users to read the data. An exclusive lock prevents other users from
accessing the data in any way.
9. Context-sensitive help means that if a user is having trouble and asks for help, the DBMS will
provide assistance for the particular feature being used at the time the user asks for help.
11. The DBA installs the DBMS, makes any changes to its configuration when they are required,
determines whether it is appropriate to install a new version of the DBMS when it becomes avail-
able, applies any vendor fixes to problems, coordinates problem resolution, and coordinates the
users so that their needs are satisfied without unduly affecting other users.
13. The DBA does some of the training of computer users. The DBA coordinates other training, such
as that provided by software vendors.
15. The production system is the hardware, software, and database for the users; the test system is a
separate system that programmers use to develop new programs and modify existing programs.
17. If users access only certain fields in a table, splitting the table results in smaller tables than the origi-
nal; the smaller amount of data moves faster between disk and memory and across a network.
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