SYS364

Architecture

Today’s Agenda

System ArchitectureProcessing Methods

On-line, Batch Centralized, De-centralized

Networking LAN/WAN/MAN Client/Server, File/Server

System Architecture

Refers to the Logical design and physical structure of a system Includes hardware, software, design

and processing methods

Environment & Platform Server Farm with UNIX(s) + Apache AS/400 with Websphere + NT

partitions

Processing Methods

Environment and/or Platform refer to a specific combination of hardware and software Influences system architecture Reinforces bias (when all you’ve got is a

hammer, everything looks like a nail) Becomes religious (but there is no

“one true” platform)

…just a few years ago

Two predominant environments Mainframes with terminal access Stand alone PC’s running one

program at a time

Today

The Internet connects everything Businesses are more dynamic than ever

Competitive pressure: e-commerce, 24/7 Corporate “right sizing” Mergers

Employees at all levels satisfy their own information needs – IT provides users with the technology, tools and resources Requires that systems be cost effective,

flexible and user-friendly

Impact on Analyst’s strategyBusiness operational requirementsMatch software to business process Level of integration with outside

systems EDI, XML, information/transaction exchange

Level of access for customers and suppliers into your platform Internet, telephony, call centers

On-line Data Processing

Transactions are processed completely when and where they occur

Users interact directly with the information system programs (not forms)

Programs update DB directly & immediately(input verification is critical to system integrity)

system availability is crucial Consider cost of downtime, manual

backup procedures

Batch Data ProcessingData is collected and processed in

batches, logically and physically.Data captured, then entered,

then input.May be more efficient than on-lineTypically used for large amounts of

data that must be processed on a routine schedule

What in case study is batch?

Batch Data Processing

Transactions are collected and processed periodically

Computer operators can run batch programs on a pre-determined schedule without user involvement

Payroll, Accounting close offData Warehouse, EIS, DSS updatesEDI

Level of Automation Volume: How much info is there? Volatility: How often does info

change? Timeliness: When does matter? Forms and batch processing PDA & handheld data collection

devices With wireless modems

Online screens everywhere

Centralized SystemsServer or Host

Mainframe and terminals e.g. IBM “big iron”, AS/400 and large

UNIX In the past, slow + $$$

communications networks limited remote data entry/input

Clustered systems Many identical systems with load

balancing, fail-over. e.g. Server farms. A horror when it’s time to

upgrade/update.Heterogeneous environments

Variety of platforms, use middleware

Distributed Systems

For business, computing is distributed geographically, connected by networks

Local and regional tasks are performed by decentralized computers

Summary uploads to central officeMay use Client/Server model

Distributed Systems Design

processing involves local and central data Data may be stored closer to users and

reduce network traffic Easily scalable – new storage sites can be

added without affecting network operation Less likely to experience a catastrophic failure …what about security? …network management? Database replication and synchronization

issues

Distributed Processing Today

Distributed CPUs SETI@Home DistributedScience Entropia

Distributed Storage (Peer-to-Peer) Napster Gnutella

Networks and the Net

The value of a network is the square of the number of things connected to it. — Metcalfe's law for Bob Metcalfe, the inventor of Ethernet and 3COM.

The value of the Net is the number of groups people on the network can form. Reid’s Law

Moore's Law= processing power doubles every 12-18 months

Metcalfe's Law = the value of n items in a network is proportional to n^2. I.e. the number of one-to-one connections.

Reed's Law: Net's value comes from its enabling of groups, I.e. the number of distinct subgroups that can form in a set of N members is 2^N

n = people n(2)-n = connections 2(n)-n-1 = groups2 2 1 3 6 4 4 12 11 5 20 26 6 30 57

10 90 1,013 100 9,900 1,267,650,600,228,230,000,000,000,000,000

1,000 999,000 1.072E+30110,000 99,990,000 #NUM!

100,000 9,999,900,000 #NUM!1,000,000 999,999,000,000 #NUM!

10,000,000 99,999,990,000,000 #NUM!100,000,000 9,999,999,900,000,000 #NUM!

1,000,000,000 999,999,999,000,000,000 #NUM!

The Net Intranet, extranet, internet Accessibility – browsers make presentation

layer independent of the platform’s software/hardware/operating systems

Low cost communications Widely implement standards (HTML, XML) Security slowly getting better Reliability – no guarantees yet Throughput – last mile problem Volatile standards and tools

Local Area Networks (LANs)/ Wide Area Networks (WANs) LANs

Hardwire a group of PCs together in a limited area to a server

WANs Uses a combination of phone lines, fiber optic

cables, microwave transmission and satellites to connect PCs and LANs into a network that can span the globe

X25, Frame Relay, ATM (Asynch Xfer Mode) Internet built on TCP/IP

MANs (Metropolitan Area Networks) New Ethernet wireless standard

Network IssuesSoftware licensingTraffic and BandwidthSecurity and FirewallsTopology, Configuration, Protocol

These issues need an expert(I.e. your friends in CNS program)

Client/Server Systems Divides processing between one or

more clients and a central server A client handles the user interface

Data entry Editing Data query

A server handles Data access Processing Database management functions

Benefits of Client/Server

? Easily scalable (up or down) to meet changing business needs ?

? Transfer of expensive mainframe systems to less expensive clients ?

In practice, benefits are dubiousand many C/S projects failed

Is a browser on the Web closer to Client/Server or Mainframe/Terminal?

Systems Design CompletionSystem Design Specification

Created before the next SDLC Phase, Implementation Detailed costs Staffing Scheduling

Oriented to Programmers so they know what to do

Oriented to Users so they know what they are getting

Approvals of the Systems Design Specification Users approve all report and output

screen designs, menu and data entry screens, source documents

IS Management will approve staffing, costs, hardware and software and effects on the operating environment

Other management – does the new system meet business objectives?

Technical and Management Presentations Programmers/operators/IS staff IS Management Company management

Possible outcomes Proceed with development Perform additional work on the design

phase Terminate the project

Summary

ArchitectureProcessingNetworkingCompleting the Design Phase of

the SDLC