systems analysis & design 7 th edition chapter 9

Systems Analysis & Design

7th Edition

Chapter 9

22

Chapter Objectives

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, cost-benefit issues, and performance

Compare in-house e-commerce development to packaged solutions

33

Chapter Objectives

Explain the difference between online and batch processing

Define network topology, and provide examples of hierarchical, star, bus, and ring network models

Describe wireless network standards, advantages, and disadvantages

44

Chapter Objectives

Explain network protocols and licensing issues

Explain performance measurement, fault management, backup, and disaster recovery

Describe the systems design specification

55

Introduction

An effective system combines elements into an architecture, or design, that is flexible, cost-effective, 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, and processing methods

66

System Architecture Checklist

The analyst must consider seven specific issues that will affect the architecture choice

– Enterprise resource planning (ERP)

– Initial and total cost of ownership (TCO)

– Scalability

– Web integration

– Legacy system interface requirements

– Processing options

– System security

77


Enterprise Resource Planning (ERP)

– The objective of ERP is to establish a company-wide strategy for using IT resources

– Advantage: it describes a specific hardware and software environment ( platform) that ensure connectivity and easy integration of future system including in house software and commercial packages

– Supply chain management

88


Initial Cost and TCO

– Ask questions like the following• If in-house development was selected as the best

alternative initially, is it still the best choice?

• If a specific package was chosen initially, is it still the best choice?

– Answers might affect the initial cost and TCO for the proposed system

99


Scalability

– Scalability, also called extensibility, refers to a system’s ability to expand, change or downsize easily to meet the changing need of a business enterprise

– Especially important in implementing systems that are volume-rated, such as transaction processing systems

1010


Web Integration

– An information system includes applications

– Web-centric architecture that follows internet design protocols and enables a company to integrate the new application into its e-commerce strategy.

– Avoids many of the connectivity and compatibility problems that typically arise

– IBM uses E-marketplaces to describe internet based solutions that allow seller and buyers to automate procurement process and achieve substantial benefits

1111


Legacy System Interface Requirements

– 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

1212


Processing Options

– In planning the architecture, designers also must consider how the system will process data - online or in batches

– Provision must be made for backup and speedy recovery in the event of system failure

1313


Security Issues

– Security is a concern at every stage of system development

– Web-based systems introduce additional security concerns

1414

Planning the Architecture

Every information system involves three main functions:

– Data storage and access methods

– Application programs to handle the processing logic

– An interface that allow users to interact with system.

– Depending on the architecture the three function are performed on a server, on a client, or are divided between the server and the client.

1515


Servers

– Server is a computer that supplies data, processing services, or other support to one or more computers called client

– The term mainframe architecture typically describes a multiuser environment where the server is significantly more powerful than the clients

1616


– Server-based processing• In a centralized design, the remote user’s keystrokes

are transmitted to the mainframe, which responds by sending screen output back

• Today mainframe architecture used in credit card company or in bank.

1717


Clients– Stand-Alone Computing

• Stand-alone computing was inefficient and expensive

• Maintaining data on individual workstations raised major concerns about data security, integrity, and consistency

• It was impossible to protect and back up valuable business data, and companies were exposed to enormous risks

• This led to data inconsistency and unreliability

1818


– Local and wide area networks• Most of the companies resolved the problems of

stand alone computing by joining clients into local area network that allows sharing of data and hardware recourses.

• A wide area network (WAN) spans long distances and can connect LANs that are continents apart

• The network is transparent

• Compared to mainframe architecture, distributed systems increase concerns about data security and integrity

1919


Clients

– Client-based processing

2020

Client/Server Architecture

Overview

– Client/server architecture refers to system that divide processing between one or more networked clients and a central server.

– In typical client/server system, the client handles the entire user interface, including data entry, data query, and screen presentation logic.

– The server stores the data and provides data access and database management functions.

2121


Overview

– The early client/server system was expensive.• Few clear standards exist

• client needed powerful hardware and software to handle shared processing tasks.

• Many companies had an installed base of mainframe data, called legacy data, which was difficult to access and transport to a client/server environment

– The client/server concept continues to expand to include clients and servers outside the organization

2323

Client/Server Architecture Client/Server Design Styles

– Depends on the style the processing is divided between the server and the clients

– The nature of communication is depends on the type of the server

• A database server process individual SQL commands.

• The transaction server handles a set of SQL commands.

• An object server exchanges object messages with clients.

• A web server sends and receives Internet based communication.

2424


• A web server sends and receives Internet based communication.

2525


Types of Clients: Fat and Thin

– A fat client also called a thick client design locates all or most of the application processing logic at client.

– A thin client design locates all or most of the processing logic at the server.

– The table in next slide describes the characteristics of the fat and thin clients.

2626


Types of Clients: Fat and Thin

2727


Client/Server Tiers

– Two-tier designs• The user interface resides on the client, all data resides

on the server, and the application logic can run either on the server or on the client or be divided between the client and server.

– Three-tier design – n-tier designs• The user interface runs on the client and the data stored

on the server, a middle layer process the client requests and translates them into data access commands that can be understood and carried out by the server

2828


Client/Server Tiers

– Three-tier design – n-tier designs• Think of the middle layer as an application server,

because it provides the application logic, or business logic

• The middle layer is more efficient and cost-effective in large-scale systems

2929


Middleware

– Enables the tiers to communicate and pass data back and forth

– Provides a transparent interface that enables system designers to integrate dissimilar software and hardware

– Can integrate legacy systems and Web-based applications

3030


Cost-Benefit Issues– Client/server systems enable the firm to scale

the system in a rapidly changing environment– Client/server computing also allows

companies to transfer applications from expensive mainframes to less expensive client platforms

– Client/server systems reduce network load and improve response times

3131


Client/Server Performance Issues– In contrast to the centralized system, a

client/server design separates applications and data

– Client/server systems must be designed so the client contacts the server only when necessary

3232


Client/Server Performance Issues– Another issue is the data storage. Data can

be stored in in more than one location using Distributed database management system (DDBMS) . DDBMS has the following advantages:

• Data stored closer to users can reduce network traffic

• The system is scalable, so new data sites can be added without reworking the system design

• The system is less likely to experience catastrophic failure

3333


Client/Server Performance Issues– DDBMS has also the following

disadvantages:• It can be more difficult to maintain controls and

standards when data is stored in various locations• The architecture of DDBMS is more complex

and difficult to manage.

3434

Internet-Based Architecture

Developing E-Commerce Solutions In-House

3535


Packaged Solutions and E-commerce Service Providers

– Many vendors offer ready to use systems for companies

– Another alternative is to use an application service provider (ASP)

– Must consider whether the advantage of lower initial cost outweighs the disadvantage of reduced flexibility later on

3636


Corporate Portals

– A corporate portal can provide access for customers, employees, suppliers, and the public

• Oracle and SAP offer powerful enterprise portal software

3737

Processing Methods

Online Processing– Online systems handles transactions when

and where they occur and provide output directly to users

– Example can be an airline reservation system and ATM system.

3838

Processing Methods

3939

Processing Methods

Online Processing– Online processing systems have four

typical characteristics:1. The system processes transactions completely

when and where they occur2. Users interact directly with the information

system3. Users can access data randomly4. The information system must be available

whenever necessary to support business functions

4040

Processing Methods

Batch Processing

– In a batch processing system, data is collected and processed in groups, or batches

– The IT operations group can run batch programs on a predetermined schedule without user involvement; and Batch programs require significantly fewer network resources than online systems

4141

Processing Methods

Combined Online and Batch Processing

– Online processing offers an inherent advantage because data is entered and validated as it occurs

– Online processing is more expensive

– Backup and recovery for online processing is more difficult

– In many situations, batch processing is cost-effective, less vulnerable to system disruption, and less intrusive

4242

Processing Methods

Combined Online and Batch Processing

– An example can be the Point of Sale (POS)

4343

Network Models

A network allows the sharing of hardware, software, and data resources in order to reduce expenses and provide more capability to users.

When planning a network design, you must consider network terms and concepts, including the OSI model, network model tools, network topology, network protocol, licensing issues, and wireless network.

4444

Network Models

The OSI Reference Model– The Open System Interconnection (OSI) model

which describes how data actually moves from an application on one computer to an application on another network, consists of seven layers

• Network layer: defines network addresses and determines how data is routed over the network

• Data link layer: defines specific methods of transmitting data over the physical layer, such as defining the start and end of a data block

• Physical layer: contains physical components that carry data, such as cabling and connecters

4545

Network Models

– Each layer performs specific function, as follow:

4646

Network Topology

– Ring network:• Resembles a circle of

computers that communicate with each other.

• Data flows in only one direction

• One disadvantage is if a device fails, the devices downstream from the failed device cannot communicate with network

4747

Network Topology

– Hierarchical network:• One or more powerful

servers control the network

• An example is retail chain, with central computer that stores data about sales activity and inventory levels and local computer handle store level operations.

4848

Network Topology

– Bus network:• A single communication path

connects the network server, departmental server, workstations, and peripheral device

• An advantage is that devices can be attached or detached from the network at any point without disturbing the rest of the network.

• Disadvantage is that the performance can decline as more devices added

4949

Network Topology

– Star network:• Has a central computer with

network devices connected to it

• At the center of the star which is called hub, a central server manages the network

• Disadvantage is that the entire network is depend on the central computer.

5050

Network Models

Network Protocols and Licensing Issues

– The network must use a protocol

– A popular network protocol is Transmission Control Protocol/Internet Protocol (TCP/IP)

– A familiar example of a TCP/IP protocol is the file transfer protocol (FTP)

5151

Network Models

Wireless Networks

– A wireless local area network, or WLAN

– Uses 802.11 protocol that is developed by Institute of Electrical and Electronics Engineers (IEEE)

– This standard referred to Wi-Fi which stands for wireless fidelity

– Although they have many advantages, wireless networks pose special concerns with regard to system security

5252

Wireless Networks

– Bluetooth is another wireless communication that is very popular for short distance wireless communication

– On addition to 802.11 protocols for LANs, IEEE is working on 802.16 standards which is communication protocol for MANs (metropolitan area networks) these specification that IEEE calls Wireless MAN™ - WiMAX are expected to enable wireless multimedia applications with a range of up to 30 miles

5353

System Management and Support

Performance Management– Performance management tools are designed to

collect information about system resources and activity levels

– Firms such as NetScout Systems offer comprehensive performance management packages

– The NetScout Web site mentions studies that show network delays cost the industry more revenue than actual stoppages

5454


Fault Management, Backup, and Disaster Recovery

– Fault management• Includes monitoring the system for signs of

trouble, logging all system failures, diagnosing the problem, and applying corrective action

5555


Fault Management, Backup, and Disaster Recovery– Backup and disaster recovery

• Backup• Recovery• Disaster recovery plan• Backup and recovery planning depends on the

type of system involved

5656


Fault Management, Backup, and Disaster Recovery

– Backup and disaster recovery• Another common strategy is to use a RAID

(redundant array of independent disks) system

• RAID systems are called fault-tolerant because the failure of any disk does not disable the system

• Experienced IT professionals often note that the three most important system security tools are backup, backup, and more backup

5757

Systems Design Completion System Design Specification

– A typical system design specification uses a structure similar to the following:1. Executive summary (brief over view of the job)

2. System components (design of input/output, data, and network)

3. System environment (constrains, or conditions, affecting the system)

4. Implementation requirements (start up process, initial data entry, training requirement and software test)

5. Time and cost estimates

6. Appendices provide supplemental material

5858

Systems Design Completion

User Approval– Users must review and approve the interface

design, report and menu designs, data entry screens, source documents, and other areas of the system that affect them

– When the system design specification is complete, you distribute the document to a target group of users, IT department personnel, and company management

5959


Presentations– The presentations give you an opportunity to

explain the system, answer questions, consider comments, and secure final approval

– The first presentation is to the systems analysts, programmers, and technical support staff members

– Your next presentation is to department managers and users from departments affected by the system

6060


Presentations– The final presentation is for company

management– Key objective: to obtain management’s

approval and support for the next development step

– Management might reach one of three decisions: proceed with systems development, perform additional work on the systems design phase, or terminate the project

6161

Chapter Summary

An information system combines hardware, software, data, procedures, and people into a system architecture

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

6262

Chapter Summary

Compared to file server designs, client/server systems are more scalable and flexible

In implementing a design, an analyst should consider e-commerce strategies, the availability of packaged solutions, and corporate portals, which are entrances to a multifunction Web site

The primary processing methods are online and batch processing

6363

Chapter Summary

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

Chapter 9 complete

systems analysis & design 7 th edition chapter 9

Documents