Estimating Software Maintenance
SEER for Software, uses sophisticated software total ownership model modeling including all the information from development (people, process, technology, defects, scope, etc.) and specifics about the maintenance such as the rigor and amount of the software to be maintained.
The figure Maintenance Staffing Plus Block Changes illustrates how maintenance is often higher in the early years than later, assuming the system remains relatively stable. Of course block changes, major changes with significant functionality (innovation) often occur, causing increases in staffing. Those block changes are often estimated and managed as enhancements to existing systems, in addition to the maintenance. The following equation (simplified to fit the scope of this blog) approximates the steady state (staff) maintenance (when the maintenance flattens)
Figure Maintenance Staffing Plus Block Changes
SteadyStateMainteanceStaff Level = 0.393469*Complexity^-0.35*((MaintSize)/MaintCte)^1.2*MaintQuality
Complexity ranges from 28(vlo-) to 4 (ehi+), so complexity^-.35 increases from 0.31 to 0.61 as you increase complexity
MaintSize is how much of the system size must be maintained, usually total size, but can be effective size, adjusted from maintenance growth, change and sites.
MaintCte is the effective technology rating (People, Process, Products) using the maintenance sensitivities
MaintQuality is “Maintenance Rigor”which ranges from 0.6 to 1.2
Also a classic rough order of magnitude rule of thumb from Barry Boehm’s original COCOMO for determining annual maintenance effort can also be useful:
Annual Maintenance Effort = (Annual Change Rate) * (Original Software Development Effort)
The quantity Original Software Development Effort refers to the total effort (person-months or other unit of measure) expended throughout development, even if a multi-year project.
The multiplier Annual Change Rate is the proportion of the overall software to be modified during the year. This is relatively easy to obtain from engineering estimates. Developers often maintain change lists, or have a sense of proportional change to be required even before development is complete.
Thank you for reading “Dan on Estimating”, if you would like more information about Galorath’s estimation models, please visit our contact page or call us at +1 310 414-3222.
Related posts:
- Software Maintenance: Costly And Controllable It always amazes me when I hear someone say they can estimate software maintenance just by taking a factor of...
- Reducing Software Maintenance and Total Ownership Costs Over 75% of the costs of software are in software maintenance. To address this I (Dan Galorath) participated in a...
- $500 Billion IT Debt For Deferred Maintenance Gartner Group has reported that the IT Debt is about $ 500 Billion, the cost of deferred maintenance with that...
- Estimating IT Projects SEER for IT was built to provide estimating abilities for IT Infrastructure and IT services. SEER for Software provides the...
- Estimating The Cost of Software Independent Verification & Validation (IV&V) Since IV&V is a level of effort activity (purchase a much as you want) people can buy as much or...
Comments
Leave a Reply
Project Prediction Infographic
