System Architecture & Hardware Configurations

Dr. D. Bilal

IS 592

Spring 2005

System Architecture

There are two major system architectures:HierarchicalClient/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

BenefitsSee Bilal, 2002, pp. 33-34.

DisadvantagesSee Bilal, 2002, p. 34.

Options for Hardware Configurations

Non-networked (a.k.a. stand-alone)AdvantagesDisadvantages

Difference between stand-alone hardware configuration and stand-alone software configuration.

Options for Hardware Configurations

Networked: LAN-basedAdvantagesDisadvantages

Networked: WAN-basedAdvantages 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