Datasheet

10
Part I: Basic Concepts
What Is a Database
Management System?
Glad you asked. A database management system (DBMS) is a set of programs
used to define, administer, and process databases and their associated
applications. The database being managed is, in essence, a structure that you
build to hold valuable data. A DBMS is the tool you use to build that structure
and operate on the data contained within the database.
You can find many DBMS programs on the market today. Some run only on
mainframe computers, some only on minicomputers, and some only on
personal computers. A strong trend, however, is for such products to
work on multiple platforms or on networks that contain all three classes of
machines. An even newer trend is to distribute data over a storage area
network (SAN) or even to store it out on the Internet.
A DBMS that runs on platforms of multiple classes, large and small, is called
scalable.
Whatever the size of the computer that hosts the database — and regardless
of whether the machine is connected to a network — the flow of information
between database and user is always the same. Figure 1-1 shows that the
user communicates with the database through the DBMS. The DBMS masks
the physical details of the database storage so that the application only has
to concern itself with the logical characteristics of the data, not with how the
data is stored.
Figure 1-1:
Block
diagram of
a DBMS-
based
information
system.
Application
Program
User
User
Interface
DBMS Database