Software Application Maintenance in software engineering is the modification of a software product after delivery to correct faults, to improve performance or other attributes.
A common perception of maintenance is that it merely involves fixing defects. However, one study indicated that the majority, over 80%, of the maintenance effort is used for non-corrective actions.
This perception is perpetuated by users submitting problem reports that in reality are functionality enhancements to the system. More recent studies put the bug-fixing proportion closer to 21%.
The key software maintenance issues are both managerial and technical.
Key management issues are:
- Alignment with customer priorities
- Estimating costs
Key technical issues are:
- Limited understanding
- Impact analysis
- Maintainability measurement
Software maintenance is a very broad activity that includes error correction, enhancements of capabilities, deletion of obsolete capabilities, and optimization. Because change is inevitable, mechanisms must be developed for evaluation, controlling and making modifications.
So any work done to change the software after it is in operation is considered to be maintenance work. The purpose is to preserve the value of software over the time. The value can be enhanced by expanding the customer base, meeting additional requirements, becoming easier to use, more efficient and employing newer technology. Maintenance may span for 20 years, whereas development may be 1-2 years.
We categorize maintenance activities into four classes:
- Adaptive – modifying the system to cope with changes in the software environment (DBMS, OS).
- Perfective – implementing new or changed user requirements which concern functional enhancements to the software
- Corrective – diagnosing and fixing errors, possibly ones found by users.
- Preventive – increasing software maintainability or reliability to prevent problems in the future.