Transcript 592_05hw

System Architecture &
Hardware
Configurations
Dr. D. Bilal
IS 592
Spring 2005
System Architecture
There are two major system
architectures:
Hierarchical
 Client/Server

Hierarchical
Architecture
All processing and activities are
controlled by the host system (e.g.,
large scale computer or mainframe,
mid-range computer or miniframe)
Remote computers connected to the
host system have limited functions
(input/output)
Hierarchical
Architecture
Remote computers connected to the
host system emulate “dumb” terminals
in communicating with the host system.
“Dumb” terminals have no or limited
processing capabilities.
Client/Server
Architecture
A client is a user’s desktop, personal
computer, or workstation
A server is a dedicated computer in a
network shared by multiple users.

More than one server can exist in this architecture
(e.g., database server, Web server, application
server, e-mail server)
Client/Server
Architecture
A computing architecture in a Local
Area Network (LAN) or a Wide Area
Network (WAN) environment where the
clients on the network perform certain
processing functions when requesting
information from a server in the
network.
Client/Server
Architecture
Uses TCP/IP to establish
communications between clients and
servers.
Clients handle the user interface (e.g.,
screen formatting, display of results,
input/output), and make requests and
send them to the application server.
Client/Server
Architecture
The server searches for the requested
information and sends the results to the
client.
The server performs database management,
information retrieval, transaction and
processing tasks.
The server delivers access to files,
applications, and network communications.
Client/Server
Architecture
This architecture differs from the
traditional file server design.
File server model:

when a user requests information from a server,
the entire database file is downloaded in the
computer making the request, resulting in slow
communication between the user’s computer and
the server.
Client/Server
Architecture
In a file server model, part of the
automation software is not loaded onto
the user’s computer (or client). The
entire software are loaded onto the
server only, and updates take place in
the server.
Client/Server
Architecture
A client may connect to one or more servers
(an OPAC server, a Web server, etc. ).
A server may connect to multiple clients
concurrently.
Client/Server
Architecture
Each client that is connected in a
client/server network must have part of
the automation software (e.g., user
interface) loaded onto its hard disk that
allows it to perform certain application
tasks.
Client/Server
Architecture
If all OPACs in a network must have
access to the Web, all clients must have
a Web browser. Similarly, if all clients
must provide access to e-mail, they
must have the e-mail client software
loaded.
Client/Server
Architecture
Servers may be large scale computers,
mid-range computers, or high-speed
microcomputers.
True client/server means that the
application was originally designed to
run on a network (LAN or WAN).
In the library
environment…
The Z39.50 protocol is used besides the
TCP/IP Protocol.
The Z39.50 is employed to facilitate sharing
information between clients and servers over
the Web.

Purpose:

To link heterogeneous automated systems on the Web
so that users can access them independent of the
software or platform in place (Mac or PC).
Types of Client/Server:
Two-Tier
Database processing tasks are done in the
server.
Application processing tasks are done in the
client requesting the information.

A request is generated in the client and
transmitted to the server. The Database
Management System that resides on the server
searches for the desired information and transmits
the results of the request to the client.
Types of Client/Server:
Three-Tier
Used when applications are in high demand.
An additional server is used for application
processing tasks.
Both the client and the additional server
perform application processing tasks.
The other server performs the database
management tasks (searching, retrieval, etc.).
Types of Client/Server:
Thin Clients
Computer terminals rather than desktop
computers.
They do little or no data processing
tasks.
They process information input/output.
Used to lower PCs and Macs cost used
in a network.
Types of Client/Server:
Thin Clients
Thin clients may be used as e-mail
stations, Web access stations, and/or
OPACs stations.
Thin clients can co-exist with thick or fat
clients in a network.
Client/Server
Architecture
Benefits

See Bilal, 2002, pp. 33-34.
Disadvantages

See Bilal, 2002, p. 34.
Options for Hardware
Configurations
Non-networked (a.k.a. stand-alone)
Advantages
 Disadvantages

Difference between stand-alone
hardware configuration and stand-alone
software configuration.
Options for Hardware
Configurations
Networked: LAN-based
Advantages
 Disadvantages

Networked: WAN-based
Advantages
 Disadvantages

The ASP Model
ASP (Access Service Provider)
Used to outsource network
maintenance and troubleshooting to a
vendor
Vendor does database installation and
update
Fee-based service