ITPEC FE Subject A April 2025 Question 43
An IT service is provided under the conditions below. What is the maximum downtime in hours that satisfies the SLA during a service period of one (1) month? Here, the number of business days in one (1) month is 30, and no maintenance or other scheduled downtime of the service is performed during the service period.
[Conditions of the SLA]
- •The service period is from 8:00 AM to 10:00 PM on business days.
- •The availability should be 99.5% or more.
Explanation
2.1 hours — availability in an SLA is measured over the agreed service hours, not over the whole calendar.
- •Service hours per day: 8:00 AM to 10:00 PM = 14 hours
- •Service hours per month: 14 × 30 = 420 hours
- •Allowed downtime at 99.5% availability: 420 × (1 − 0.995) = 420 × 0.005 = 2.1 hours
Check: (420 − 2.1) ÷ 420 = 0.995, exactly the SLA limit.
Answer (b)
Why not others:
- •(d) 3.6 — counts 24 hours a day for 30 days, 720 × 0.005 = 3.6, although downtime outside 8:00 AM to 10:00 PM is not service time
- •(c) 3.0 — too much: (420 − 3) ÷ 420 ≈ 0.9929, below the required 99.5%
- •(a) 0.3 — satisfies the SLA (about 99.93%) but is not the maximum; the question asks for the largest downtime that still meets 99.5%
Key rule: Maximum downtime = agreed service hours × (1 − required availability); first work out which hours the SLA actually covers.
Service Management · AI-written, may contain errors
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