1 systems analysis & design systems implementation & support is 431: lecture 11...

1

Systems Analysis & Design

Systems Implementation &

Support

IS 431: Lecture 11

http://www.csun.edu/~dn58412/IS431/IS431_SP15.htm

CSUN Information Systems

IS 431 : Lecture 11 2

Systems Implementation & Support in SDLC


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.


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.


System Construction and Implementation


Tasks inConstruction Phase


Tasks in Construction Phase

1. Build and Test Networks

2. Build and Test Databases

3. Install and Test New Software Package

4. Write and Test New Programs


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


2. Build and Test DatabasesImplement database schemaTest with sample dataDeliver unpopulated database structureRoles

– 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


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


4. Write and Test New Programs

Develop in-house programs– Reuse available software components in library– Write new components– Test– Document


Clarifies business requirements

– System Designer Clarifies program design and integration requirements

– Application Programmers Writes and tests in-house software


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.


Tasks inImplementation Phase


Tasks inImplementation Phase

1. Conduct System Test

2. Prepare Conversion Plan

3. Install Databases

4. Train Users

5. Convert to New System


1. Conduct System TestTest network, databases, purchased software, new in-

house software, and existing software to make sure it all works together.


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


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


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 testing certifies that the system is free of errors and is ready to be placed into operation.


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


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


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


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


Installation/Conversion Strategies

Abrupt cutover

Parallel conversion

Location (Pilot) conversion

Staged (Phased) conversion

New System

Old system

Old System New System




Installation/Conversion Strategies …

Risk

Cost

AbruptCutover

LocationConversion

StagedConversion

ParallelConversion


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.

Support vs. Operation


The Context of Systems Operation and Support


Systems Development, Operation, and Support


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.


Systems Support Activities


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.


Causes of “Bugs”

Poorly validated requirements.Poorly communicated requirements.Misinterpreted requirements.Incorrectly implemented requirements or designs.Simple misuse of the programs.


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.


System Maintenance Tasks


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.


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.


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).


Technical Support

Being on call to assist usersTypical 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


System Enhancement Triggers

New business problemsNew business requirementsNew technology requirements (including hardware

and software upgrades)New design requirements


System Enhancement Activities


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.


System Obsolescence

All systems degrade over time (entropy)At some point, not cost-effective to support and

maintainLeads to a new systems development projectNew cycle of SDLC

1 systems analysis & design systems implementation & support is 431: lecture 11...

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