Software maintenance

A présentation on
Maintenance

Definitions
The act of keeping, or the expenditure required to
keep, an asset in condition to perform efficiently the
service for which it is used.

• The modification of a product, after
delivery,
– to correct faults,
– to improve performance or other
attributes,
– or to adapt the product to a changed
environment.

Types of Maintenance
All maintenance activities have been grouped under four classes.
They are-

1.Corrective maintenance:

2.Adaptive maintenance

3.Preventive maintenance

4.Perfective maintenance

Corrective maintenance: Reactive modification of a
software product performed after delivery to correct
discovered problems.

• system: response to equipment
malfunctions
• characteristics:
• - inefficient maintenance department
• - unpredictable equipment operation
• - all maintenance work unplanned
• example: light bulb replacement
• results: steady degradation of equipment
performance
• maintenance department
responsibility:
• - respond to emergencies
• - get production back on line

• Adaptive maintenance: Modification of a software product
performed after delivery to keep a software product usable
in a changed or changing environment.
System: equipment design is based on
minimal maintenance requirements.
Characteristics- close relationship with
equipment suppliers.

example: roadways ,websites etc
results: continually improving equipment
maintenance department
responsibility:
- input to equipment design
- minimize & eliminate maintenance
requirements

Preventive maintenance: Modification of a software product
after delivery to detect and correct latent faults in the
software product before they become effective faults.
system:
- periodic adjustments & checks
- periodic replacement of worn parts
- periodic overhaul
characteristics:
- more predictable
- more efficient
example: changing oil & filters
results: maintain level
of equipment
maintenance department
responsibility:
- checking, replacing & overhauling
- perform checks during maintenance

Perfective maintenance: Modification of a software
product after delivery to improve performance
or maintainability.
system: periodic measurement & trending of equipment process
characteristics:
- predictable maintenance requirements
-planned & scheduled equipment repairs

example: software updates and service packs.
results: maintain equipment performance
with minimal disruption to production
maintenance department responsibility:
- log equipment repairs
- trend data
- predict equipment repair cycles

maintenance processes
There are six software maintenance
processes which are as follows:

1) The implementation processes
contains software preparation and
transition activities, such as the
conception and creation of the
maintenance plan, the preparation
for handling problems identified
during development, and the
follow-up on product configuration
management.

2) The problem and modification analysis process, which is executed
once the application has become the responsibility of the
maintenance group. The maintenance programmer must analyze
each request, confirm it (by reproducing the situation) and check its
validity, investigate it and propose a solution, document the request
and the solution proposal, and, finally, obtain all the required
authorizations to apply the modifications.

3. The process considering the implementation of the modification
itself.
4. The process acceptance of the modification, by confirming the
modified work with the individual who submitted the request in
order to make sure the modification provided a solution.

5. The migration process is
exceptional, and is not part of daily
maintenance tasks. If the software
must be ported to another platform
without any change in
functionality, this process will be used
and a maintenance project team is
likely to be assigned to this task.
6. Finally, the last maintenance
process, also an event which does not
occur on a daily basis, is the
retirement of a piece of software.

Software maintenance
Software maintenance is the process of
changing a system after it has been delivered.

• Modifying a program after
it has been put into use.
• Maintenance does not
normally involve major
changes to the system’s
architecture.
• Changes are implemented
by modifying existing
components and adding
new components to the
system.

Software Breakdown Causes
• basic conditions neglected
• inadequate skills
• operating standards not followed
• deterioration unchecked
• inherent design weakness

Need for software maintenance
• Maintenance to repair software faults
– Changing a system to correct deficiencies in the way
meets its requirements.
• Maintenance to adapt software to a different
operating environment
– Changing a system so that it operates in a different
environment (computer, OS, etc.) from its initial
implementation.
• Maintenance to add to or modify the system’s
functionality
– Modifying the system to satisfy new requirements.

Optimal maintenance
Its the discipline which is concerned with maintaining a
system in a manner that maximizes profit or minimizes cost.
• Cost functions depending on the reliability and
maintainability characteristics of the system
determine the parameters of interest to minimize.
• Parameters often considered are
– the cost of failure,
– the cost per time unit of "downtime",
– the cost (per time unit) of corrective maintenance,
– the cost per time unit of preventive maintenance an
– the cost of repairable system replacement

Maintenance costs
Maintenance costs are usually greater than
development costs by a factor of 2 to 100.
• The costs arise from both technical and nontechnical
factors.
 A deployed system is expensive to change .
 High cost of breaking an already working system.
 Maintenance costs increase over time and as the system
evolves.

Reasons:
Maintenance changes ,degrades the original system
structure.
Aging software results in high support costs.

Maintenance cost factors
Team stability
Maintenance costs are reduced if the same staff are involved with
them for some time.
Contractual responsibility
The developers of a system may have no contractual responsibility
for maintenance so there is no incentive to design for future
change.

Staff skills
Maintenance staff are often
inexperienced and have limited
domain knowledge.

Program age and structure
As programs age, their structure
is degraded and they become
harder to understand and
change.

Strategies to reduce maintenance costs:

-Correct slight defects in parts and jigs.
- Ensure basic equipment conditions are
maintained
- Review basic
operations
- Conduct physical
analysis
- Adopt an analytical
approach

Distribution of maintenance effort

Fault rep air
(17%)

Fun ction ality
So ftw are
additio n or
adaptatio n
mo dification
(18%)
(65 %)

Source:www.wikipedia.com

Maintenance Problems

• Someone else's program.
• Developer not available.
• Proper documentation doesn't exist.
• Not designed for change.
• Maintenance activity not highly regarded.

Maintenance is inevitable
• The system requirements are likely to change while the system is
being developed because the environment is changing. Therefore a
delivered system won't meet its requirements.
• Systems are tightly coupled with their environment. When a system is
installed in an environment it changes that environment and
therefore changes the system requirements.
• Therefore systems MUST be maintained if they are to remain useful in
an environment.

The Rewards of Maintenance

• Maintenance is a thankless task in every way:
• Maintainers deal with dissatisfied users.
• If the user were happy, the product would not
need maintenance.
• The user’s problems are often caused by the
individuals who developed the product, not the
maintainer.
• The code itself may be badly written.
• Post delivery maintenance is despised by many
software developers.

• Unless good maintenance service is provided, the client
will take future development business elsewhere.
• Post delivery maintenance is the most challenging
aspect of software production —and the most
thankless.
• The user frequently does not understand that
maintenance can be difficult, or impossible for some
requests.

Conclusion

• Maintenance is a major cost for software and must be
planned for during the entire life cycle.

• Design workflow —use information-hiding techniques
• Implementation workflow — good coding style

• Documentation must be complete, correct, and current.

• During maintenance, maintainability must not be
compromised.

• Maintenance is so critical and challenging that the best
people should be put on the task and rewarded accordingly.

Software maintenance

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