Databases Reference
In-Depth Information
8.
Security.
What types of security features does the DBMS provide? Does the DBMS support encryp-
tion, password support, and authorizations rules? Does the DBMS provide a view mechanism that
can be used for security? How difficult is it to bypass the security controls?
9.
Integrity.
What type of integrity constraints does the DBMS support? Does the DBMS support
entity integrity (the fact that the primary key cannot be null) and referential integrity (the prop-
erty that values in foreign keys must match values already in the database)? What types of data
integrity does the DBMS support? Does the DBMS support any other types of integrity
constraints?
10.
Replication and distributed databases.
Does the DBMS support replication? If so, does the
DBMS allow partial replicas (copies of selected rows and fields from tables in a database)? And
how does the DBMS handle updates to the same data from two or more replicas? Can the DBMS dis-
tribute a database, that is, divide the database into segments and store the segments on differ-
ent computers? If so, what types of distribution does the DBMS allow and what types of procedure
support for distribution does the DBMS provide?
11.
Limitations.
What limitations exist with respect to the number of tables and the number of fields
and rows per table? How many files can you open at the same time? (For some databases, each
table and each index is in a separate file. Thus, a single table with three indexes, all in use at the
same time, would account for
four
files. Problems might arise if the number of files you can open
is relatively small and many indexes are in use.) On what types of operating system and hard-
ware is the DBMS supported? What types of local area networks (LANs) can you use with the
DBMS? (A
local area network (LAN)
is a configuration of several computers connected together
that allows users to share a variety of hardware and software resources. One of these resources is
the database. In a LAN, support for concurrent update is very important because many users
might be updating the database at the same time. The relevant question here, however, is not how
well the DBMS supports concurrent update but which of the LANs you can use with the DBMS.)
12.
Documentation and training.
Does the vendor of the DBMS supply printed or online training
manuals? If so, how good are the manuals? Are they easy to use? Is there a good index? Is a tuto-
rial, in either printed or online form, available to assist users in getting started with the system?
Is online help available? If so, does the DBMS provide general help and context-sensitive help?
(
Context-sensitive help
means that if a user is having trouble and asks for help, the DBMS will pro-
vide assistance for the particular feature being used at the time the user asks for the help.) Does
the vendor provide training classes? Do other companies offer training? Are the classes on-site
or off-site? Are there classes for the DBA and separate classes for programmers and others? What
is the cost for each type of training?
13.
Vendor support.
What type of support does the vendor provide for the DBMS, and how good is
it? What is the cost? What is the vendor's reputation for support among current users?
14.
Performance.
How well does the DBMS perform, where performance is a measure of how rap-
idly the DBMS completes its tasks? This is a difficult question to answer because each organiza-
tion has a different number of users and a different mix of transactions and both factors affect
how a DBMS performs. One way to determine relative performance among DBMSs is to look into
benchmark tests that various organizations have performed on several DBMSs. Benchmarking
typically is done in areas such as sorting, indexing, and reading all rows and then changing data val-
ues in all rows. For example, the Transaction Processing Performance Council (
www.tpc.org)
pro-
vides the results of database benchmark tests to its members. Beyond using benchmarks, if an
organization has some specialized needs, it may have to set up its own benchmark tests. Does the
DBMS provide a performance monitor that measures different types of performance while the
DBMS is operational?
15.
Portability.
Which operating systems can you use with the DBMS? What types of files can you
import or export? Can the DBMS link to other data sources, such as files and other types of
DBMSs? Does the DBMS provide Internet and intranet support? (An
intranet
is an internal com-
pany network that uses software tools typically used on the Internet and the World Wide Web.)
16.
Cost.
What is the cost of the DBMS and of any additional components the organization is plan-
ning to purchase? Is additional hardware required? If so, what is the associated cost? If the orga-
nization requires a special version of the DBMS for a network, what is the additional cost? What
is the cost of vendor support, and what types of support plans are available?
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