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Systems Analysis & Design

CSUN Information Systems. Systems Analysis & Design. http://www.csun.edu/~dn58412/IS431/IS431_SP14.htm. Systems Implementation & Support. IS 431: Lecture 11. Systems Implementation & Support in SDLC. Systems Implementation & Support.

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Systems Analysis & Design

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  1. CSUN Information Systems Systems Analysis & Design http://www.csun.edu/~dn58412/IS431/IS431_SP14.htm Systems Implementation & Support IS 431: Lecture 11

  2. Systems Implementation & Support in SDLC IS 431 : Lecture 11

  3. Systems Implementation & Support • Construction/Implementation and Operation/Support in SDLC. • System/applications and system acceptance tests. • System installation/conversion strategies. • System support: maintenance, recovery and enhancement. IS 431 : Lecture 11

  4. System Construction and Implementation Systems Construction: the development, installation, and testing of system components. Systems Implementation: the delivery of that system into production , up and running. IS 431 : Lecture 11

  5. System Construction and Implementation IS 431 : Lecture 11

  6. Tasks inConstruction Phase IS 431 : Lecture 11

  7. Tasks in Construction Phase • Build and Test Networks • Build and Test Databases • Install and Test New Software Package • Write and Test New Programs IS 431 : Lecture 11

  8. 1. Build and Test Networks • Often system build around existing networks. • If system calls for new network functionality, must by built and tested prior to programs that use that it. • Roles • Network designer • Designs LAN and WAN connectivity • Network administrator builds and tests • Network architecture standards • Security • Systems analyst • Facilitates • Ensures that business requirements are not compromised IS 431 : Lecture 11

  9. 2. Build and Test Databases • Implement database schema • Test with sample data • Deliver unpopulated database structure • Roles • System Users • Provide and/or approve test data • Database Designer/Programmer • Build tables, views, stored procedures (if relational database) • Database Administrator • “Tune” database for optimum performance • Security • Backup and recovery • Systems Analyst • Build non-corporate, applications-oriented database • Ensures business requirements compliance IS 431 : Lecture 11

  10. 3. Install and Test New Software • If system requires purchased or leased software, must be installed and tested. • Roles • Systems Analyst • Clarifies business requirements • System Designer • Clarifies integration requirements • Network Administrator • Install software package • Software Vendor/Consultant • Assist in installation and testing • Applications Programmers • Test according to integration requirements IS 431 : Lecture 11

  11. 4. Write and Test New Programs • Develop in-house programs • Reuse available software components in library • Write new components • Test • Document • Roles • Systems Analyst • Clarifies business requirements • System Designer • Clarifies program design and integration requirements • Application Programmers • Writes and tests in-house software IS 431 : Lecture 11

  12. Levels of Testing Stub test - a test performed on a subset of a program. • Individual events or modules of a program. • Testing of an isolated subset of a program. Unit or program test – a test performed on an entire program. • All the events and modules tested as an integrated unit. Systems test – a test performed on an entire system • Ensures that application programs written and tested in isolation work properly when integrated into the total system. IS 431 : Lecture 11

  13. Tasks inImplementation Phase IS 431 : Lecture 11

  14. Tasks inImplementation Phase • Conduct System Test • Prepare Conversion Plan • Install Databases • Train Users • Convert to New System IS 431 : Lecture 11

  15. 1. Conduct System Test • Test network, databases, purchased software, new in-house software, and existing software to make sure it all works together. • Roles • Systems Analyst • Develops system test data • Communicates problems and issues • System Builders (database, network, programmers) • Resolve problems revealed during testing • System Owners and users • Verify whether or not system operates correctly • May result in return to construction phase • Iterate until successful system test IS 431 : Lecture 11

  16. Systems Acceptance Test • Systems Acceptance Test – a test performed on the final system wherein users conduct a verification, validation, and audit test. • Uses real data over an extended time period • Extensive test that addresses: verification testing, validation testing, and audit testing. • Verification Testing runs the system in a simulated environment using simulated data. • Alpha testing • Simulated environment using simulated data • Checks for errors and omissions regarding end-use and design specifications IS 431 : Lecture 11

  17. Systems Acceptance Test • Validation testing runs the system in a live environment using real data. • Beta testing • Live environment using real data • Testing: • Systems performance (throughput and response time) • Peak workload performance • Human engineering • Methods and procedures • Backup and recovery • Audit testingcertifies that the system is free of errors and is ready to be placed into operation. IS 431 : Lecture 11

  18. 2. Prepare Conversion Plan • Plan for how to convert from old system to new system. • How to install and populate databases • How to train users • Finalize documentation • Conversion issues • Roles • System analyst/Project manager • Develop a detailed conversion plan • Steering committee • Approves plan and timetable IS 431 : Lecture 11

  19. 3. Install Databases • Populate new system databases with existing data from old system • Generally have to restructure data as it is populated • Must confirm that data is translated correctly • Roles • Application programmers • Write (or use) special programs to extract data from existing databases and populate new databases • Systems analyst/designer • Calculate database sizes and estimate time for installation IS 431 : Lecture 11

  20. 4. Train Users • System users trained and provided with documentation • Roles • System analyst • Plan trainings • Conduct trainings • Write documentation • Help users through the learning period • System owners • Approve release time for training • System users • Attend training • Accept system IS 431 : Lecture 11

  21. 5. Convert to New System • Ownership transfers from analysts and builders to end users. • Roles • Systems analyst/Project manager • Carries out conversion plan • Correct shortcomings • Measure system acceptance • System owners • Provide feedback • System users • Provide feedback IS 431 : Lecture 11

  22. Installation/Conversion Strategies New System • Abrupt cutover • Parallel conversion • Location (Pilot) conversion • Staged (Phased) conversion Old System Old system New System New System Old System New System Old System IS 431 : Lecture 11

  23. Installation/Conversion Strategies … Abrupt Cutover Risk Location Conversion Staged Conversion Parallel Conversion Cost IS 431 : Lecture 11

  24. Support vs. Operation Systems support is the on-going technical support for users, as well as the maintenance required to fix any errors, omissions, or new requirements that may arise. Systems operation is the day-to-day, week-to-week, month-to-month, and year-to-year execution of an information system’s business processes and application programs. An operational system is a system that has been placed into operation. Also called a production system. IS 431 : Lecture 11

  25. The Context of Systems Operation and Support IS 431 : Lecture 11

  26. Systems Development, Operation, and Support IS 431 : Lecture 11

  27. Important Data Stores of the System • The repository is a data store(s) of accumulated system knowledge—system models, detailed specifications, and any other documentation accumulated during systems development. • The program library is a data store(s) of all application programs. • The business data is all those data stores of the actual business data created and maintained by the production application programs. IS 431 : Lecture 11

  28. Systems Support Activities IS 431 : Lecture 11

  29. System Support Activities • Program Maintenance corrects “bugs” or errors that slipped through the system development process. • System Recovery is the restoration of the system and data after a system failure. • Technical Support is any assistance provided to users in response to inexperience or unanticipated situations. • System Enhancement is the improvement of the system to handle new business problems, new technical problems, or new technology requirements. IS 431 : Lecture 11

  30. Causes of “Bugs” • Poorly validated requirements. • Poorly communicated requirements. • Misinterpreted requirements. • Incorrectly implemented requirements or designs. • Simple misuse of the programs. IS 431 : Lecture 11

  31. System Maintenance Objectives • To make predictable changes to existing programs to correct errors. • To preserve those aspects of the programs that were correct, and to avoid “ripple effects” of changes that may adversely affect the correctly functioning aspects. • To avoid, as much as possible, the degradation of system performance. • To complete the task as quickly as possible without sacrificing quality and reliability of the system. IS 431 : Lecture 11

  32. System Maintenance Tasks IS 431 : Lecture 11

  33. System Maintenance Tasks • Validate the problem. • Benchmark the program. • A test script is a repository of test cases to be executed against all program revisions. • Study and debug the program to fix: • Poor program structure. • Unstructured (or poorly structured) logic. • Prior maintenance (so-called “ripple” effects.) • Dead code. • Poor or inadequate documentation. • Test the program. • Version control is a process whereby a librarian program keeps track of changes made to programs to facilitate backtracking. IS 431 : Lecture 11

  34. Types of Testing • Unit testing (essential) ensures that the stand-alone program fixes the bug without undesirable side effects to the program. • System testing (essential) ensures that the entire application, of which the modified and unit tested program was a part, still works as a complete system. • Regression testing (recommended) extrapolates the impact of the changes on system performance (throughput and response time) by analyzing before-and-after performance against the test script. IS 431 : Lecture 11

  35. System Recovery Activities • Direct: Client-side (end-user) recovery and/or instruction directly from the systems analyst. • Indirect: Server-side recovery through a system administrator. • Indirect: Database recovery and rollback through a database administrator. • Indirect: Network recovery or fix through a network administrator. • Indirect: Technical or vendor assistance to correct a hardware problem. • Direct: Detection of a software bug (which triggers systems maintenance). IS 431 : Lecture 11

  36. Technical Support • Being on call to assist users • Typical tasks: • Routinely observing the use of system • Conducting user-satisfaction surveys and meetings • Changing business procedures for clarification • Providing additional training • Logging enhancement ideas and requests in repository IS 431 : Lecture 11

  37. System Enhancement Triggers • New business problems • New business requirements • New technology requirements (including hardware and software upgrades) • New design requirements IS 431 : Lecture 11

  38. System Enhancement Activities IS 431 : Lecture 11

  39. System Enhancement Tasks • Analyze enhancement request. • If appropriate, make the quick fix. • e.g., report writing • Recover the existing physical system. • Database recovery and restructuring • Program analysis, recovery, and restructuring • Repeat appropriate phases and tasks of the original development methodology. IS 431 : Lecture 11

  40. System Obsolescence • All systems degrade over time (entropy) • At some point, not cost-effective to support and maintain • Leads to a new systems development project • New cycle of SDLC IS 431 : Lecture 11

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