SYS364 Architecture

Today’s Agenda  System Architecture  Processing 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 everythingInternet  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 strategy  Business operational requirements  Match 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 Processing  Data is collected and processed in batches, logically and physically.  Data captured, then entered, then input.  May be more efficient than on-line  Typically 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 off  Data Warehouse, EIS, DSS updates  EDI

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 Systems  Server 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 office  May 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 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

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 Issues  Software licensing  Traffic and Bandwidth  Security and Firewalls  Topology, 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 dubious and many C/S projects failed  Is a browser on the Web closer to Client/Server or Mainframe/Terminal?

Systems Design Completion  System 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  Architecture  Processing  Networking  Completing the Design Phase of the SDLC