Software Engineering IT402 SATUDY MATERIL.pptx

software Maintenance

1. Software Maintenance

2. Main Work Error Correction Deletion of obsolete code. Enhance Capabilities. Optimization.

3. Types of Maintenance Corrective Maintenance: If error arise correct it. 20% of total software maintenance phase. Adaptive Maintenance: New technology adaption. 25% of total software maintenance phase. Preventive Maintenance: Before arising any problem take action. 5% of total software maintenance phase. Perfective Maintenance: Make optimize and perfect. 5% of total software maintenance phase.

4. Mean Time Between Failure (MTBF) It is the average time available for a system or component to perform its normal operations between failure. MTBF=(Sum of operational time/total number of failures)

5. Mean Time To Repair It is the average time required to repair a failed component. MTTR= (Sum of down time periods)/total number of failures Availability: MTBF/(MTBF+MTTR)

6. Problem A machine that runs for 24 hours. During that time, it failed twice and each time it took 1 hour to get it back up and running. Find the MTBR and MTTR.

7. Solution MTBF= 22/2 = 11 MTTR= 2/2 = 1 Availability: 11/12 = 0.91= 91.6%

8. Availability: MTBF/(MTBF+MTTR) MTBF= 25*24 = 600 hours MTTR= 6 hours Availability: 600/606 =0.9909 = 99.009%

9. MTBF= 30*24 = 720 hours MTTR = 12 hours Availability: 720/732 = 0.98 = 98.3%