1. PHASE 3: SYSTEMS DESIGN
Chapter 8
System Architecture

2. 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 considerations
Describe the impact of the Internet on system architecture 3

3. Chapter Objectives
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 3

4. Chapter Objectives
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

5. 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, processing methods, and security 4

6. System Architecture Checklist
A systems analyst must approach system architecture with an overall checklist
Enterprise resource planning (ERP)
Initial and total cost of ownership (TCO)
Scalability
Web integration
Legacy system interface requirements
System security
Processing options

7. System Architecture Checklist
Enterprise Resource Planning (ERP)
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
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
ERP:
ERP provides centralized, integrated software applications to help manage and coordinate the ongoing activities of the functional units of an enterprise, including manufacturing and distribution, accounting, finance, sales, product planning, and human resources.
In CIO magazine, 5 major reasons companies undertake ERP were cited:
Integrate financial information
Integrate customer order information
Standardize and speed up mfg processes
Reduce inventory
Standardize HR information
ERP also helps companies:
Reduce the workforce by eliminating manual tasks and duplication
Reduce information system development staff by using packaged solutions
Improve customer service through better logistics
Improve data integrity through a common database
Supply Chain Management:
Many companies extend their ERP systems to their suppliers and customers through supply chain management. This can help companies achieve faster response, better customer service, and lower operating costs. RFID allows companies to track inventory items through the supply chain.

8. System Architecture Checklist
Initial Cost and TCO
Ask questions like the following
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
Ask:
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?
Have any new types of outsourcing become available?
Have any significant technical developments occurred that could affect proposed projects?

9. System Architecture Checklist
Scalability
Scalability, also called extensibility
Especially important in implementing systems that are volume-related, such as transaction processing systems
Web Integration
An information system includes application programs, also called applications
Web-centric
Scalability:
Refers to system’s ability to expand, change or downsize to meet changing business needs.
Ensures that a system designed, built, or purchased when a company is small is adequate when the company doubles in size. When a system no longer scales, it must be replaced with a new system.
Web Integration:
A Web-centric architecture follows Internet design protocols and enables a company to integrate the new application into its e-commerce strategy (whether on the internet, co. intranet, or extranet)
A web-based application avoids many of the connectivity and compatibility problems that arise when different h/w environments are involved. (external partners use web browsers to import/export data)

10. 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 legacy systems involves analysis of data formats and compatibility
The analyst must know if the new application eventually will replace the legacy system
Legacy System Interface Requirements:
Legacy systems must be considered when evaluating physical design.
The ability of a system to share information with other systems sometimes is called interoperability.
Systems with interoperability are said to be open, while systems without interoperability are said to be closed.
An interoperable system not only can interface with legacy systems, it also is more likely to be able to interface with new systems that are introduced as a result of company acquisitions or mergers.

11. System Architecture Checklist
Processing Options
Online or Batch
24/7
Backup and Recovery
Processing Options:
In planning the architecture, designers also must consider how the system will process data – storage, network, processing resources are different: for instance an online order entry system Vs. a monthly billing system will be much different. Then you must consider will this system be:
24/7 – will system be running 24 hours a day, seven days a week
Provision must be made for backup and speedy recovery in the event of system failure

12. System Architecture Checklist
Security Issues
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

13. Planning the Architecture
Every information system involves 3 main functions:
Data Storage and Access Methods
Application Programs
Interface
The 3 functions may be performed on a …
Server OR
Client OR
Divided between Server and Client
Every information system involves three main functions:
data storage and access methods
application programs to handle the processing logic
an interface that allows users to interact with the system
Depending on architecture, the 3 functions are performed on a …
Server
Client
Divided between Server and Client
You will need to determine where the functions will be carried out and the advantages and disadvantages of each design approach.

14. Client/Server Architecture
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
A server, sometimes called a host computer, controls access to the hardware, software, and other resources on a network and provides a centralized storage area for programs, data, and information.
Mainframe Architecture – A system design where the server performs all the processing.
Centralized Architecture – A server that supports a large number of clients at various locations is called a centralized system.
Background:
In the 1960s, mainframe architecture was the only design around. Everything was done at a central location. Users had no input or output capability, except for printed reports distributed by corp. IT.
As networks advanced and became affordable, companies installed terminals at remote locations, so users could enter and access data from anywhere. This terminal included the keyboard and display screen but no processing capability. (pg. 369)
In the 1980s, microcomputer use exploded. Users ran their own Word Processing, Spreadsheet, and Database applications w/o IT assistance in stand-alone computing.
Stand-alone computing raised major concerns about data security, integrity, and consistency. Without central storage, stand-alone computing was impossible to protect and back-up.

15. Client/Server Architecture
Overview
Client/server architecture
File Sharing Architecture – The problem of stand-alones was solved with LANs or FSAs and joining these individual stand-alones or clients. However, this type of architecture requires significant resources since the data file is sent back to the requestor as you can see here.
Client/Server:
Rapid increases in transmission capacities, significant reductions in cost, and standardized methods of connecting and working with networks have allowed distributed computing to become the preferred method of deploying business applications. Client/server architecture is a popular distributed computing strategy. (Distributed system is one or more connected LANs or WANs. WAN-long distance, continent apart)
Client/Server Architecture consists of:
The systems that divide processing between one or more networked clients and central server.
The clients are other computers on a network that rely on the server for its resources.

16. Client/Server Architecture
Client/Server Design Styles
Many forms
Database Server
Transaction Server
Web Server
Client/server designs can take many forms, depending on the type of server and the relationship between the server and the clients
Servers that perform a specific task, such as those shown in this figure, sometimes are called dedicated servers
Database Server – processes individual SQL commands
Transaction Server – handles a set of SQL commands
Web Server – sends and receives Internet-based communications

17. Client/Server Architecture
Types of Clients: Fat and Thin
Fat client - Thick client
Thin client
Comparison:
Thin  better performance
Thick  more processing
Fat Client:
AKA 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
Most IT experts agree that thin client designs provide better performance, because program code resides on the server, near the data
In contrast, a fat client handles more of the processing and must access and update the data more often
Look at pg

18. Client/Server Architecture
Client/Server Tiers
Two-tier design
Three-tier design
Middle layer
Two-tier design – Early client/server designs were called 2 tier designs.
Here, the user interface resides on the client, all data resides on the server, and the application logic can run on the server, the client or the client and server.
Three-tier design – Recently popular.
In a 3 tier design, because the layers are relatively independent of one another, they can be placed on different computer systems, with network connections and middleware servers to bind them into a single application.
User interface runs on a client
Data stored on server
Middle layer between client and server - processes client requests and translates them into commands understood by the server.
Think of middle layer as an application server, because it provides the application logic, or business logic
Three-tier designs also are called n-tier designs – may use more than 1 intermediate layer.
The middle layer is more efficient and cost-effective in large-scale systems because it reduces the data server’s workload and relieves clients of complex processing tasks.
Look at pg. 375, fig to compare architectures.

19. Client/Server Architecture
Middleware -Cost-Benefit Issues
Scale the system
Transfer applications
Improve response times
Client/server systems enable the firm to scale the system in a rapidly changing environment
Example: Company like Centene that specializes in adding a new Medicaid plan every year with
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
Middleware sometimes is called plumbing because it connects two sides of an application and passes data between them. Common types of middleware include teleprocessing monitors, remote procedure calls (RPCs), object request brokers (ORBs), and distributing computer environment (DCE).

20. Client/Server Architecture
Client/Server Performance Issues
Separation of server-based data and networked clients
Separates applications and data
Client contacts server only when necessary
Distributed Database Management System (DDBMS)
Although there are many advantages over file-based systems, there can be performance issues of client-server architecture that relate to the separation of server-based data and networked clients
In contrast to the centralized system where the command is executed by the server’s own CPU, a client/server design separates applications and data. Therefore, processing is more efficient in centralized because data and program instructions travel together on an internal bus.
Client/server systems must be designed so the client contacts the server only when necessary and makes as few trips as possible. Otherwise, bog down.
Distributed database management system (DDBMS)
Data can be stored in more than one location using DDBMS. Advantages:
Data stored closer to users can reduce network traffic
New data sites added without reworking system design
Data stored in various locations
System less likely to experience catastrophic failure
Disadvantages:
Data security
Difficult to maintain controls and standards, when in various locations
More complex and difficult to manage

21. Internet-Based Architecture
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
The Internet has had a huge impact on system architecture. Experts agree that the key to the Internet alternative is flexibility. Implementing e-commerce applications via the Web, an intranet, or an extranet offers:
Accessibility — Web browsers and Internet connections are almost everywhere, so applications are available to a large number of users.
Low cost — The WANs that form the Internet backbone primarily are government-funded, so connections can be purchased at low cost.
Wide availability — Web standards are well-known, so server, client, and application development software is widely available and relatively inexpensive.
Potential negative aspects include problems with security, reliability, throughput, and changing standards.

22. Internet-Based Architecture
Developing E-Commerce Solutions In-House
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 e-commerce environment
Advantages:
Satisfies unique business requirements
Minimizes changes in business procedures and policies
Meets constraints of existing systems
Meets constraints of existing technology
Develops internal resources and capabilities
Disadvantages:
Increases costs
Requires more time to implement
Lacks proven reliability and performance benchmarks
Requires more technical development staff
Demands in-house development of upgrades
Lacks input from other companies

23. Internet-Based Architecture
Packaged Solutions and E-Commerce Service Providers
Turnkey systems
Application service provider (ASP)
Does lower initial cost outweigh disadvantage of reduced flexibility?
Many vendors offer turnkey systems for companies
Another alternative is to use an application service provider (ASP)
With packaged solution, must consider whether the advantage of lower initial cost outweighs the disadvantage of reduced flexibility later on

24. Internet-Based Architecture
Corporate Portals
A portal is an entrance to a multifunction Web site
A corporate portal can provide access for customers, employees, suppliers, and the public

25. Network Models The OSI Reference Model – consists of 7 layers
Application layer
Presentation layer
Session layer
Transport layer
Network layer
Data link layer
Physical layer
Before looking at Network Topologies, we will briefly discuss the OSI (Open system interconnection) model which describes how data moves from an application on one computer to an application on another networked computer.
The OSI model is a logical model that consists of 7 layers. Each layer performs a specific function:
Application layer: provides network services requested by local workstation
Presentation layer: assures that data is uniformly structured and formatted for network transmission
Session layer: defines control structures that manage the communications link between computers
Transport layer: provides reliable data flow and error recovery
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
Data goes down through the layers on the transmitting computer, then up through the layers on the receiving computer.

26. Network Models Network Topology Hierarchical network
The way a network is configured is called the networked topology. LANs and WANs are arranged in 4 configurations:
Hierarchical
Star
Bus
Ring
Concepts are the same regardless of the size of the network, but the implementation is different
Hierarchical Network
One computer (mainframe usually) controls entire network.
Satellite computers or servers control lower levels of processing and network devices.
Example: retail chain  central computer stores sales activity and inventory levels, local computers handle store operations. Stores transmit data to central computer. Central analyzes stock levels and coordinates supply chain mgmt system.
Disadvantage: if business adds additional processing levels, network becomes more complex and expensive to operate and maintain

27. Network Models Network Topology Star network Star network:
Central computer with network devices connect to it.
At center is the hub or central computer that manages the network.
Star networks are fairly easy to install and maintain.
Nodes can be added to or removed from the network with little or no disruption.
If one node fails, the other nodes can continue to operate normally.
This topology is used when network control is important, because all traffic must flow into and out of the hub.
Central computer does not have to serve as primary data storage location; it can serve as network coordinator that enables other devices to transmit and receive stored data from each other.
A failure in any star network cable will only take down one computer's network access and not the entire LAN. (If the hub fails, however, the entire network will fail.)
Disadvantage:
Entire network depends on the central computer.
Most large star networks have backup systems in case of a failure.

28. Network Models Network Topology Bus network Bus network:
A single communication path connects the mainframe comuter, server, workstations, and peripheral devices.
Information is transmitted in either direction from any workstation to another workstation, and any message can be directed to a specific device.
Bus networks are popular on LANs because they are inexpensive and easy to install.
Although it can be wired to look like a star network with a wiring hub at the center, a bus network can be identified by the single cable that exists inside the hub.
Advantage:
Devices can be attached or detached at any point w/o disturbing the rest of the network.
Failure in one workstation does not necessarily affect other workstation on the network
Disadvantage:
Performance can decline as more users and devices are added, because all message traffic must flow along the central bus.
If more than a few dozen computers are added to a network bus, performance problems will likely result If more than a few dozen computers are added to a network bus, performance problems will likely result.
This does not occur in the treelike flow of a hierarchical network or the hub-and-spoke of a star network where network traffic in one path does not affect traffic elsewhere on the network.

29. Network Models Network Topology Ring network Ring Network:
Resembles a circle of computers that communicate with each other.
Although a ring network can span a larger distance than a bus network, it is more difficult to install.
A ring network is used when processing is performed at local sites rather than at a central location
For example, users accessing computers in the Acctg, Personnel, and Engineering depts perform the processing for individual functions and then use the ring network to exchange data with other computers on the network.
Although the ring topology primarily is used for LANs, but it also can be used in WANs.
Data flows in only one direction on a ring network.
Found in some offices or school buildings
Disadvantage:
If a network device (Pc or printer) fails, the devices downstream cannot communicate with the network
A second difficulty is that if two computers are sending messages at the same time, the messages can become garbled

30. Network Models Network Topology Other topologies

31. 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)
Protocols or standards must be used which govern network data transmission.
Transmission Control Protocol/Internet Protocol (TCP/IP).
Originally developed by US Dept of Defense.
Backbone of internet
TCP/IP manages the transmission of data by dividing it up into small pieces, or packets. Each packet contains data, as well as the information about the sender, the recipient, and the sequence, which is used to reassemble the data.
Example usage: FTP  a way to copy files from one computer to another over a TCP/IP network, such as the Internet or an intranet.
Consider s/w licensing restrictions in network design since some vendors limit number of users or computers that can access computers simultaneously.

32. Systems Design Completion
System Design Specification
Baseline
Contents vary depending on company standards
You do not have to turn this in
System Design Specification:
aka technical design spec or detailed design spec presents the complete design for the new information system, along with detailed costs, staffing, and scheduling
Baseline against which operational system will be measured
Users can understand this document
Contents vary depending on company standards and complexity of system

33. Systems Design Completion
User Approval of …
Interface design
Report and menu designs
Data entry screens
Source documents
Other
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

34. Systems Design Completion
Presentations
Systems analysts, programmers, technical staff
Department managers and users
Company management
Objective: Obtain management’s approval/support
At the end of the systems design phase, you will give 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
Key objective: to obtain management’s approval and support for the next development step

35. Chapter Summary
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 49

36. Chapter Summary Any questions?
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? 49