1. System Architecture & Hardware Configurations
Dr. D. Bilal
IS 582
Spring 2009

2. System Architecture Two major system architectures: Hierarchical
Client/Server

3. Hierarchical Architecture
Processing and activities are controlled by the host system
Remote computers connected to host system have limited functions
(input/output)

4. 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.

5. 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, server)

6. Client/Server Architecture
A computing architecture in a LAN or WAN environment
Clients on network perform certain processing functions when requesting information from a server in the network

7. Client/Server Architecture
TCP/IP to establish communications between clients and servers
Clients handle the user interface
screen formatting, display of results, input/output
make requests and send them to the application server

8. 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.

9. 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.

10. File Server Architecture
Software programs are loaded onto the server only
Updates are performed in server
Updates take less time to install than those in client/server architecture

11. 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.

12. 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 client hard disk to perform certain application tasks.

13. 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 , they must have the client software loaded on them.

14. 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).

15. Client’s Functions/Tasks
Handles the user interface.
Translates the user's request into the desired protocol.
Sends the request to the server.
Waits for the server's response.
Presents the results to the user.

16. 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.

17. 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.

19. 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.).

21. 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.

22. Types of Client/Server: Thin Clients
May be used as stations, Web access stations, and/or OPACs stations.
Can co-exist with thick or fat clients in a network.

23. Options for Hardware Configurations
Non-networked (a.k.a. stand-alone)
Advantages
Disadvantages
Difference between stand-alone hardware configuration and stand-alone software configuration.

24. Options for Hardware Configurations
Networked: LAN-based
Advantages
Disadvantages
Networked: WAN-based