System Maintenance

1
System Maintenance

• Modifications or corrections made to an
  information system after it has been released to
  its customers
• Changing an information system while it is in
  operation
• Evolving an information system to adapt to
  changing business conditions and user needs

2
Systems Development Lifecycle Models

• Waterfall
• Iterative Enhancement
• Prototyping
• Spiral model
• Rapid Application Development
• Inspections and Reviews

3
Systems Lifecycle
Software Engineering Lifecycle
Project Identification Selection
Feasibility Analysis
Project Initiation Planning
Requirements
Design
Analysis
Logical Design
Coding Integration
Physical Design
Test
Implementation
Installation
Maintenance
Maintenance
4
IEEE Maintenance Process

• Modification request
• Classification and Identification
• Analysis
• Design
• Implementation
• System Test
• Acceptance Test
• Delivery

5
Categories of Maintenance

• Corrective - fixing bugs
• Adaptive - no change to functionality, but now
  works under new conditions
• Perfective - adds something new makes the system
  better
• Preventive - enhances internal structure of
  system without affecting external behavior

Enhancements
6
Maintenance Terms

• Configuration Control Board (CCB) -
  organizational unit that makes decisions about
  what proposed maintenance changes will actually
  be made
• Regression testing - testing a modified system
  with some of the test cases with which it was
  originally tested to make sure that only those
  functions that were meant to change actually
  behave differently
• Releases - planned collections of maintenance
  changes that are applied to a system before it is
  delivered to customers
• Patches - emergency fixes to a system that are
  delivered to customers between scheduled releases
• Configuration management - the process of keeping
  track of different versions of a system that have
  been supplied to different customers and that
  must be maintained separately

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Maintenance Terms (cont.)

• Ripple effect - the (usually unintended) effects
  that a change in one part of a system has on
  other parts of the system
• Impact analysis - analysis of a planned
  modification to a system in an effort to
  determine all of the components of the system
  that will be affected by the modification,
  including ripple effects
• System decay - a degradation of system structure
  and quality over time due to poorly planned and
  executed changes
• Program comprehension - the human process of
  understanding a piece of software code
• Porting - a type of adaptive maintenance in which
  a system is translated from one operating system,
  language, or platform to another

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Impact analysis

• During planning - determine modules that will
  need to be modified, to estimate time and
  resources needed
• During analysis - understand data and control
  flow in order to follow chain of ripple effects
• During design implementation - keep track of
  what ripple effects have been accounted for
• During test - known ripple effects guide testing
  further testing reveals unknown ripple effects

9
Impact Analysis Strategies

• Data flow - follow changed pieces of data
  (variables) from one module to another to see
  what other variables are affected
• Control flow - follow the call chain, i.e. what
  modules are called by affected modules
• Program slicing - based on data flow and/or
  control flow

10
Course Logistics

• Meet every Tuesday at 700pm for 2-3 hours
• Group project - small-to-medium maintenance task
• Leading class - lecture, discussion, and class
  exercises
• Exams - non-traditional
• Class participation - I take this seriously!

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Student-led Class Sessions

• Part I 30-minute (10-12 slides) lecture on
  textbook chapter
• Part II Class discussion based on 3 research
  papers
• Part III Class exercise from textbook
• By Friday send me an email with first and second
  preferences for topic, date, and part

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Information for Forming Project Teams

• Name
• Department
• Degree Program
• Programming experience (languages, length of
  experience, type of experience)
• Other skills
• Times you could meet regularly