System Architecture & Hardware Configurations Dr. D. Bilal IS 582 Spring 2007.
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Hierarchical Architecture
Processing and activities are controlled by the host system
Remote computers connected to 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
Client: a user’s computer Server: 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 LAN or WAN environmentClients on network perform certain
processing functions when requesting information from a server in the network
Client/Server Architecture
TCP/IP to establish communications between clients and servers
Clients handle the user interface screen formatting, display of results,
input/outputmake requests and send them to the
application server
Client/Server Architecture
Server searches for requested information and sends results to the client(s)
Server performs database management, information retrieval, transaction and processing tasks.
Server delivers access to files, applications, and network communications.
File Server Architecture
User requests information from a server Entire database file is downloaded in the
computer making the request results in slow communication between the
user’s computer and the server.
File Server Architecture
Software programs are loaded onto the server only.
Installing updates are done in server Updates take less time to install than
those in client/server architecture
Client/Server Architecture
One client may connect to one or more servers: OPAC server, T-mail server, and other servers
One 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 into the computer
(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.
If all clients must provide access to e-mail, they must have the e-mail client software loaded on them.
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).
Client’s Functions/Tasks
Handles the user interface. Translates the user's request into the
desired protocol. Sends the request to the server. Wait for the server's response. Present the results to the user.
Server’s Functions/Tasks
Receives a request/query from the client.
Processes the query. Returns the results back to the
client. Client presents the results to the
user.
Two-Tier
Server: Processes database tasks such as search and retrieval.
Client: Processes application tasks. 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.
The client present the information to the user on the screen.
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.
Do little or no data processing tasks. Process information (input/output). Used to lower PCs and Macs cost
used in a network.
Types of Client/Server: Thin Clients
May be used as e-mail stations, Web access stations, and/or OPACs stations.
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.
Additional information is found at: http://www.sei.cmu.edu/str/descriptions/client
server.html http://www.answers.com/topic/client-server
Options for Hardware Configurations
Non-networked (a.k.a. stand-alone)AdvantagesDisadvantages
Difference between stand-alone hardware configuration and stand-alone software configuration.
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