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