Systems Analysis & Design
(Sixth Edition)
PHASE 3: SYSTEMS DESIGN
Chapter 8
System Architecture
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Chapter Objectives
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Provide a checklist of issues to consider when
selecting a system architecture
Describe servers, server-based processing, clients,
and client-based processing
Explain client/server architecture, including tiers, costbenefit issues, and performance considerations
Describe the impact of the Internet on system
architecture
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Chapter Objectives
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Explain the difference between online and
batch processing
Define network topology, and provide
examples of hierarchical, star, bus, and ring
network models
Explain network protocols and licensing issues
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Chapter Objectives
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Explain system management tools and
techniques, including performance
measurement, fault management, backup, and
disaster recovery
Describe the systems design specification and
explain the contents of each section
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Introduction
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An effective system combines elements into
an architecture, or design, that is flexible, costeffective, technically sound, and able to
support the information needs of the business
System architecture translates the logical
design of an information system into a physical
structure that includes hardware, software,
network support, processing methods, and
security
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System Architecture Checklist
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A systems analyst must approach system
architecture with an overall checklist
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Enterprise resource planning (ERP)
Initial and total cost of ownership (TCO)
Scalability
Web integration
Legacy system interface requirements
System security
Processing options
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System Architecture Checklist
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Enterprise Resource Planning (ERP)
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The objective of ERP is to establish a company-wide
strategy for using IT resources
Describes environment – platform
Supply chain management
Initial Cost and TCO
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During the final design stage, you make decisions
that will have a major impact on the initial costs and
TCO for the new system
You should review all previous cost estimates
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System Architecture Checklist
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Initial Cost and TCO
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Ask questions like the following
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Is in-house development still best choice?
Is specific package still best choice?
New outsourcing available?
New technology available?
Answers might affect the initial cost and TCO for the
proposed system
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System Architecture Checklist
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Scalability
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Scalability, also called extensibility
Especially important in implementing systems that
are volume-related, such as transaction processing
systems
Web Integration
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An information system includes application
programs, also called applications
Web-centric
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System Architecture Checklist
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Legacy System Interface Requirements
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The new system might have to interface with one or more
legacy systems
Interfacing a new system with legacy systems involves
analysis of data formats and compatibility
The analyst must know if the new application eventually will
replace the legacy system
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System Architecture Checklist
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Processing Options
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Online or Batch
24/7
Backup and Recovery
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System Architecture Checklist
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Security Issues
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Security is a concern at every stage of system
development
The systems analyst must consider security issues
that relate to system design specifications and
determine how the company will address them
Web-based systems introduce additional security
concerns
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Planning the Architecture
Every information system involves 3 main functions:
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Data Storage and Access Methods
Application Programs
Interface
The 3 functions may be performed on a …
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Server
OR
Client
OR
Divided between Server and Client
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Client/Server Architecture
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Today’s interconnected world requires an
information architecture that spans the entire
enterprise
Whether you are dealing with a departmental
network or a multinational corporation, as a
systems analyst you will work with a
distributed computing strategy called
client/server architecture
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Client/Server Architecture
Overview
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Client/server architecture
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Client/Server Architecture
Client/Server Design Styles
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Many forms
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Database Server
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Transaction Server
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Web Server
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Client/Server Architecture
Types of Clients: Fat and Thin
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Fat client - Thick client
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Thin client
Comparison:
Thin  better performance
Thick  more processing
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Client/Server Architecture
Client/Server Tiers
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Two-tier design
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Three-tier design
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Middle layer
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Client/Server Architecture
Middleware -Cost-Benefit Issues
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Scale the system
http://www.centene.com/investors/annual_reports
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Transfer applications
Improve response times
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Client/Server Architecture
Client/Server Performance Issues
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Separation of server-based data and networked clients
Separates applications and data
Client contacts server only when necessary
Distributed Database Management System (DDBMS)
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Internet-Based Architecture
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The Internet has had an enormous impact on
system architecture
To support this trend, systems analysts must
suggest e-commerce strategies that apply
available technology and meet their
company’s business requirements
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Internet-Based Architecture
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Developing E-Commerce Solutions In-House
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If you decide to proceed with an in-house solution,
you must have an overall plan to help achieve your
goals
An in-house solution usually requires a greater initial
investment, but provides more flexibility for a
company that must adapt quickly in a dynamic ecommerce environment
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Internet-Based Architecture
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Packaged Solutions and E-Commerce
Service Providers
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Turnkey systems
Application service provider (ASP)
Does lower initial cost outweigh disadvantage of
reduced flexibility?
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Internet-Based Architecture
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Corporate Portals
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A portal is an entrance to a multifunction Web site
A corporate portal can provide access for customers,
employees, suppliers, and the public
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Network Models
The OSI Reference Model – consists of 7 layers
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Application layer
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Presentation layer
 Session layer
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Transport layer
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Network layer
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Data link layer
 Physical layer
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Network Models
Network Topology
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Hierarchical network
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Network Models
Network Topology
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Star network
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Network Models
Network Topology
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Bus network
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Network Models
Network Topology
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Ring network
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Network Models
Network Topology
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Other topologies
http://compnetworking.about.com/od/networkdesign/a/topologies.htm
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Network Models
Network Protocols and Licensing Issues
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The network must use a protocol
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A popular network protocol is Transmission
Control Protocol/Internet Protocol (TCP/IP)
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A familiar example of a TCP/IP protocol is the
file transfer protocol (FTP)
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Systems Design Completion
System Design Specification
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Baseline
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Contents vary depending on company
standards
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You do not have to turn this in
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Systems Design Completion
User Approval of …
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Interface design
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Report and menu designs
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Data entry screens
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Source documents
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Other
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Systems Design Completion
Presentations
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Systems analysts, programmers, technical staff
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Department managers and users
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Company management
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Objective: Obtain management’s approval/support
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Chapter Summary
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The analyst must consider enterprise resource planning, initial
cost and TCO, scalability, Web integration, legacy interface
requirements, security, and processing options
System security is an important concern
An architecture requires servers and clients
Compared to file server designs, client/server systems are more
scalable and flexible
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Chapter Summary
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Networks allow the sharing of hardware, software, and data
resources in order to reduce expenses and provide more
capability to users
The way a network is configured is called the network topology
The system design specification presents the complete
systems design for an information system
Any questions?
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