Estimating Software Maintenance Costs

In Software Engineering under Software cost estimation

1. Estimating Software Maintenance Costs BY K.LALITHAMBIGA IIMsc(Computer Science & Information Technology) Department of CS&IT NS College of Arts and Science Theni.

2. Estimating Software Maintenance Costs Software maintenance typically requires 40 to 60 percent, and in some cases as much as 90 percent, of the total lifecycle effort devoted to a software product. The major concerns about maintenance during the planning phase of a software projects are estimating the number of maintenance programmers that will be needed and specifying the facilities required for maintenance. A widely used rule of thumb for the distribution of maintenance activities is 60% -Enhancement 20% -Adaptation 20% -Corrections

3. In survey 487 business data processing installations, Lientz and Swanson determined that typical level of effort devoted to software maintenance was around FOR EXAMPLE: If a maintenance programmer can maintain 32KDSI, then two a maintenance programmers are required to main 64 KDSI: FSPm =(64KDSI)/(32 KDSI/FSP)=2 FSPm 50% of total lifecycle effort, The distribution of maintenance activities was 51.3% for enhancement , 23.6% for adaptation, 21.7% for repair and 3.4% for others(LIE80).

4. Boehm suggests that maintenance effort can be activity ratio , which is the number of source instruction to be added and modified in any given time period divided by the total number of instructions: Number of programmer –months required for maintenance in the corresponding time period: In enhancement is provided by an effort adjustment factor EAF, which recognizes that the effort multipliers for maintenance may be different from the effort multipliers used for development: ACT=( DSI added+ DSI modified )/ DSI total PMm =ACT * MMdev PMm =ACT *EAF* MMdev

5. Maintenance Effort Distribution

6. Source Instruction per maintenance programmer(Adapted from BOE81)

7. For Example Heavy emphasis on reliability and the use of modern programming practices during development may reduce the amount of effort required for maintenance, while low emphasis on reliability and modern practices during development may increase the difficulty of maintenance. FSP - Fulltime Software Personnel KSDI -Kilo delivered Source Instruction ACT -Activity ratio DSI -Delivered Source Instruction PM -Programmer Months EAF -Effort Adjustment Factor

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