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System Architecture

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Chapter 9: System Architecture

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CHAPTER 9:
SYSTEM
ARCHITECTUR
E

SYSTEM

ARCHITECTURE translates the logical
design of an information
system into a physical
structure that includes
hardware, software,
network support, and

SYSTEM
ARCHITECTURE
CHECKLIST

System Architecture
Checklist


Enterprise Resource Planning (ERP) –
The objective of ERP is to establish a
company- wide strategy for using IT
resources



The main advantage of ERP is that it
describes a specific hardware and software
environment, also called a platform, that
ensures connectivity and easy integration



Supply Chain Management (SCM)

System Architecture
Checklist
 Initial

Cost and TCO - 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 and ask the following
questions which can be seen in the
handouts.

System Architecture
Checklist
 Scalability

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

 Also

called extensibility.

 Especially

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

System Architecture
Checklist
Web Integration - An information system
includes applications
 program that handles the input, manage
the processing logic, and provide the
required output
 Web-centric architecture
 Avoids many of the connectivity and
compatibility problems that typically arise
 E-marketplaces


System Architecture
Checklist
 Legacy

System Interface
Requirements – The new system might

have to interface with one or more legacy
systems
 Interfacing a new system with a legacy
system involves analysis of data formats
and compatibility
 The analyst must know if the new
application eventually will replace the
legacy system

System Architecture
Checklist
 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

System Architecture
Checklist
 Security

Issues – Security threats and

defenses are a major concern to a systems
analyst


The analyst must consider security issues
that relate to system design specifications



Web-based systems introduce additional
security concerns

PLANNING THE
ARCHITECTURE

Planning the Architecture
 Servers

– is a computer that supplies data,
processing services, or other support to one
or more computers, called clients.
 Mainframe

Architecture

– a system design where the server
sometimes performs all the processing.

Planning the Architecture


Server-based Processing – Companies
installed terminals at remote locations, so
that users could enter and access data
from anywhere in the organization,
regardless of where the centralized
computer was located



Terminal – included a keyboard and
display screen to handle input and output,
but lacked independent processing
capability

Planning the Architecture
 Clients

– As PC technology exploded in
the mid-1980s and 1990s, powerful
microcomputers quickly appeared on
corporate desktops
 Users found that they could run their own
word processing, spreadsheet, and
database applications
 Companies linked the stand-alone
computers into networks

Planning the Architecture
 Stand-Alone

Computing – when an
individual user works in stand-alone
mode, the workstation performs all
functions of a server by storing,
accessing, and processing data, as
well as providing a user interface.

Planning the Architecture
 Local

and Wide Area Networks

◦ Local Area Network (LAN) – allows sharing of
data and hardware resources
◦ Wide Area Network (WAN) – spans long
distances and can connect LANs that are
continents apart
When a user access data on a LAN or WAN, the
network is transparent because a user sees the
data as if it were stored on his or her own
workstation. Company-wide systems that connect
one or more LANs or WANs are called distributed
systems

Planning the Architecture
 Client-Based

Processing

As LANs became popular, the most common LAN
configuration was a file server design. In a file
server design, also called a file sharing
architecture, an individual LAN client has a copy
of the application program installed locally,
while the data is stored on a central file server

Client/Server
Architecture

Client/Server Architecture


Client/Server Architecture - Refers to
systems that divide processing between on
or more networked clients and a central
server

Fat and Thin client
 Fat client – also called thick client, locates
all or most of the application processing
logic at the client
 Thin client – locates all or most of the
processing logic at the server

Client/Server Architecture
 Client/Server

Tiers

◦ Two-tier - UI resides on the client, all data
resides on the server and application logic
can run on either or be divided between
the two
◦ Three-tier – also called n-tier design,
has middle layer between client and server

Client/Server Architecture
 Middleware

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


Provides a transparent interface

- Can integrate legacy systems and Webbased applications

Client/Server Architecture


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

Client/Server Architecture


Client/Server Performance Issues
– In contrast to the centralized system, a
client/server design separates applications and
data
– Distributed database management system
(DDBMS)
– 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

Internet-Based
Architecture

Internet-Based
Architecture
Developing E-Commerce Solutions In-House
 Packaged Solutions and E-commerce
Service Providers
– Many vendors offer turnkey systems for
companies
– Another alternative is to use an
application service provider (ASP)
– Another option is managed hosting
– Consider the experience of other
companies in the same industry


Internet-Based
Architecture
Corporate Portals
– A corporate portal can provide access
for customers, employees, suppliers, and
the public
 Cloud Computing
– Effectively eliminates compatibility
issues
– Scaling on demand
– Requires significantly more bandwidth


Processing
Methods

Processing Methods
 Online

Processing

- Handles transaction when and where
they occur and provides output directly to
users
– Because it is interactive, online
processing avoids delays and allows a
constant dialog between the user and the
system
– Online processing also can be used with
file-oriented systems

Processing Methods
 Batch

Processing

- Data is collected and processed in
groups or batches
– The IT operations group can run batch
programs on a predetermined schedule,
without user involvement, during regular
business hours, at night, or on weekends
– Require significantly fewer network
resources than online systems

Network Models

Network Models
 Network

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

Network Models
 Open

System Interconnection
(OSI) Reference Model
– Describes how data actually moves
from an application on one computer to an
application of another networked computer
- The OSI model consists of seven layers
– Each layer performs a specific function
– Offers a set of design standards

Network Models
7

layers of OSI

◦ Application Layer
◦ Presentation Layer
◦ Session Layer
◦ Transport Layer
◦ Network Layer
◦ Data Link Layer
◦ Physical Layer

Network Models
 Network

Modeling Tools

– As you translate the OSI logical model
into a physical model of the networked
system, you can use software tools
- Microsoft Visio

Network Models
 Network

Topology – the way a network is

configured. LAN and WAN networks are
typically arranged in four patterns:
A. HIERARCHICAL NETWORK
- It mirrors the actual operational flow in the
organization
- One disadvantage of a hierarchical network is
that if a business adds additional processing
levels, the network becomes more complex
and expensive to operate and maintain

Network Models
B. STAR NETWORK
- has a central computer with network
devices connected to it
- Hub is the center and it manages the
network
- Disadvantage of the star design is that
the entire network is dependent on the
switch - However, in most large star
networks, backup switches are available
immediately in case of hardware failure

Network Models
C. BUS NETWORK
- Devices can be attached or detached
from the network at any point without
disturbing the rest of the network
- Overall performance declines as more
users and devices are added
- Today, the bus design is much less
popular

Network Models
D. RING NETWORK
- resembles a circle of computers that
communicate with each other
- One disadvantage of a ring network is
that if a network device fails (such as a PC
or a server), the devices downstream from
the failed device cannot communicate with
the network
- Multistation Access Unit (MAU)

Network Models
 Network

Protocols

– In all cases, the network must use a
protocol, a set of standards that govern
network data transmission
– Transmission Control Protocol/Internet
Protocol (TCP/IP)
– File Transfer Protocol (FTP)
 Licensing

Issues

Wireless
Networks

Wireless Networks
A

wireless local area network, or
WLAN

 Wireless

Network Standards

– 802.11
– Institute of Electrical and Electronics
Engineers (IEEE)
– Amendments
– Mbps (megabits per second)

Wireless Networks
 Wireless

Network Standards

– 802.11g
– 802.11n
– Multiple input/multiple output (MIMO)
– Multipath design
– 802.11y

Wireless Networks
 Wireless

Network Topologies

– Basic Service Set (BSS) – infrastructure
mode
– Access point
– Extended Service Set (ESS)
– Roaming
– Independence Service Set (ISS) – peerto-peer mode

Wireless Networks
 Wireless

Trends

– Wi-Fi Alliance
– Wi-Fi (wireless fidelity)
– BlueTooth
– On addition to 802.11 protocols for
LANs, IEEE is working on 802.16 standards
– MANs (metropolitan area networks)
– WiMAX

System
Management and
Support

System Management and
Support
 Performance

Management

– tools are designed to collect
information about system resources and
activity levels
- A performance management tool can
monitor system usage, capacity, and trends.
It also includes fine tuning the network
configuration or software settings to
optimize performance.

System Management and
Support
 Fault

Management

- Main concern is to detect and resolve
operational problems as quickly as possible.
- The task includes monitoring the
system for signs of trouble, logging all
system failures, diagnosing the problem and
applying corrective actions.

System Management and
Support
 Backup

– refers to copying data continuously or at
prescribed intervals
 Recovery

Procedures

– involve restoring the data and restarting the
system after an interruption
An overall backup and recovery plan is often
called a disaster recovery plan.

System Design
Completion

System Design Completion
 System

Design Specification

– A typical system design specification
uses a structure similar to the following:
1.
2.
3.
4.
5.
6.

Executive Summary
System Components
System Environment
Implementation Requirements
Time and cost estimate
Appendices

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

System Design Completion
 Presentations

– 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
– The final presentation is for company
management
– Management might reach one of three decisions:
proceed with systems development, perform
additional work on the systems design phase, or
terminate the project

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