Database Reference
In-Depth Information
8. Security. What types of security features does the DBMS provide? Does the DBMS support
encryption, password support, and authorizations rules? Does the DBMS provide a view mecha-
nism 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
distribute a database, that is, divide the database into segments and store the segments on dif-
ferent computers? If so, what types of distribution does the DBMS allow and what types of pro-
cedure 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 systems and hardware
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
tutorial, in either printed or online form, available to assist users in getting started with the sys-
tem? 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 provide 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
267
s reputation for support among current users?
14. Performance. How well does the DBMS perform, where performance is a measure of how rapidly
the DBMS completes its tasks? This is a difficult question to answer because each organization
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
values in all rows. For example, the Transaction Processing Performance Council (www.tpc.org)
provides 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 operating?
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
organization 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?
'
