Database Reference
In-Depth Information
Display
Terminal
Display
Terminal
Display
Terminal
Display
Terminal
Display
Terminal
DBMS
Teleprocessing
Monitors
Compilers
and
Interpreters
Application
Programs
Editors
Utilities
SOFTWARE
OPERATING SYSTEM
Disk
Storage
CPU
Controllers
Other I/O
units
Memory
HARDWARE
Figure 13-20
Centralized DBMS architecture.
Implementation in Client/Server Architecture
You are probably familiar with client/server computing. However, let us first review
the client/server computing model and briefly describe its features. Here is a broad
description:
•
Client/server architecture implies cooperative or distributed processing. Two or
more systems are linked through network connections.
•
There could be one or many servers on the network—print server, file server,
communications server, and relational database server. However, to the user
signing on to the computer system, the system appears to be a unified system.
•
The client system executes some parts of the application and provides the user
interface. The client system requests services from the various servers.
•
The server system provides services requested by client systems. Typically, a
relational DBMS engine runs on a server machine.
Figure 13-21 illustrates a simple client/server architecture at the logical level.
Note the various client machines attached to a communications network in a
centralized configuration.
Although many database management systems started out as mainframe
versions, now every vendor has adapted its DBMS for client/server architecture.
User interface and application programs used to reside on the mainframe computer
system. Now, these are the first programs to be moved to the client side in a
client/server configuration. Query and transaction processing performs on the
server side. The database component resides on the server side.
In a typical client/server setup, application programs and user interface software
run on the client machines. When an application program on the client side requires
a database access, it establishes a connection to the DBMS on the server side. When
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