Maintenance Phase

1
Maintenance Phase

• Chapter 16

2
The Maintenance Phase

• Changes to the software product after the
  product has been accepted by the client,
  installed and used for its intended purpose
• Maintenance is sometimes referred to as the
  Evolution of the product over time

3
Types of Maintenance

• Maintenance performed during product development
• Maintenance performed during the maintenance phase

4
Maintenance performed during product development

• Changes in client requirements before the product
  is delivered
• Fixing of faults detected before the product is
  delivered
• Modification of components to be reused in the
  product.

5
Maintenance performed during the maintenance
phase (1)

• Corrective
• Correct faults in specification, design, coding,
  documents, etc.
• Uses up 17.5 percent of maintenance time
• Perfective
• Changes made to improve the effectiveness of the
  product.
• Uses up 60.5 percent of maintenance time

6
Maintenance performed during the maintenance
phase (2)

• Adaptive
• Changes made to response to changes in the
  environment in which the product operates.
• Uses up 18 percent of maintenance time
• Others
• Uses up 4 percent of maintenance time

7
Steps in changing a product

• Determine the cause of the product failure
• In case of adaptive or corrective, determine the
  new requirements
• Repair the fault
• Test the repair
• Perform regression testing
• Update the documentation
• Describe what was changed, by whom, and when

8
Required Skills of a Maintenance Programmer (1)

• For corrective maintenance
• Exceptional debugging skills
• Ability to determine cause of failure
• Ability to function effectively without adequate
  documentation

9
Required Skills of a Maintenance Programmer (2)

• For perfective and adaptive maintenance
• Highly skilled in all areas software development
• Skilled in developing software specifications,
  design, implementation, integration and testing

10
Perception of Maintenance

• In the software development industry, maintenance
  is viewed as
• drudge work
• Thankless task
• Frustrating
• Have to deal with frustrated users
• Relegated to junior programmers
• Unglamorous
• This is why no one wants to be a maintainer

11
Management Responsibilities

• Excellent maintenance is crucial to making
  clients happy
• Managers must ensure that highly qualified
  programmers perform maintenance by
• Giving maintainer the status and salary
  commensurate with maintenance effort
• This will improve the attitude towards maintenance

12
Management of Maintenance (1)

• Initiate maintenance through
• Fault reports
• Corrective maintenance
• User report to re-create the fault
• Provides for a mechanism to changing the product
• Prioritization
• Workarounds
• Change in requirements
• adaptive and perfective maintenance

13
Management of Maintenance (2)

• Authorizing changes to the product
• Authorize maintainers to change the product
• Require maintenance SQA to test the product and
  release a new version
• Distribute the new version to users
• Ensuring maintainability
• Maintainers should plan for maintainability of
  the changes being made to the software

14
Management of Maintenance (3)

• Problem of repeated maintenance
• If the person requesting the changes a sufficient
  clout ( i.e., money and authority), changes to
  software is unavoidable
• Constant changes to the product results in
• Deviation from original design making future
  changes more difficult
• Documentations become less reliable
• Regression testing files may become outdated
• The whole product may have to be re-written

15
Reverse Engineering (1)

• If the source code is the only available
  documentation
• Use it to attempt to recreate the design and
  specification documents
• Reverse engineering
• CASE tools pretty printer or tools to construct
  flowcharts or UML diagram

16
Reverse Engineering (2)

• If the executable is the only available artifact
• Use it as a black box to reverse engineer the
  specifications, then use the reconstructed
  specification create a new version of the product
  using forward engineering

17
Reverse Engineering versus Forward Engineering

• Reverse engineering
• Takes the product from a lower level of
  abstraction to a higher level of abstraction
• From code to design to specification
• Forward engineering
• Takes the product from a higher level of
  abstraction to a lower level of abstraction
• From secification to design to code

18
Restructuring

• Takes place on the same level of abstraction
• Restructuring code
• Restructuring specifications
• Restructuring design
• Improving the product without changing its
  functionality
• Typically performed to increase maintainability

19
Testing

• Test the repairs made
• Perform regression testing
• Regression test cases may need to be modified as
  a result of the changes made

20
CASE Tools

• Version control
• Configuration tool
• MS Source Safe
• ClearCase
• sccs, rcs, cvs (UNIX)
• CCC
• Fault tracking
• DevTrack

21
Metrics

• For adaptive and perfective maintenance
• All the metrics previously discussed the other SW
  phases
• Total number of faults
• By type
• By severity
• Status of current fault reports
• How many fixed
• How many pending