Uptime / SLA Availability Calculator mechanism

Model scope

The core formulas are standard: downtime = period × (1 - availability_fraction) and availability_fraction = 1 - downtime/period. Verdict is NEEDS_REVIEW because the specification does not resolve the exact ambiguity between percentage values and normalized fractions, and it does not define the period conventions or nines-classification rules.

• The formulas are mathematically correct when availability is represented as a fraction from 0 to 1. The specification says availability percentage, but does not state whether the engine converts 99.9% to 0.999; applying the formulas directly to 99.9 produces an invalid result.
• The nines classification table is underspecified: it must define whether classifications are exact thresholds, minimum availability thresholds, or rounded labels, and how 100% availability is classified.

Units and conventions

• Availability input expressed as a percentage must be divided by 100 before use: 99.9% becomes 0.999.
• Availability must be within 0% to 100%; downtime must be nonnegative and no greater than the selected period for observed availability.
• The period and downtime must use matching units before division or multiplication.
• A year is assumed to contain 365 days in the examples; leap years require an explicit separate convention.
• A month is not a fixed duration unless the instrument explicitly selects a calendar month or a fixed 30-day month.
• A week is assumed to contain 7 days and a day 24 hours.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "mode": "allowed_downtime",
    "availability_percent": 99.9,
    "period_days": 365
  },
  "expected_outputs": {
    "availability_fraction": 0.999,
    "allowed_downtime_days": 0.365,
    "allowed_downtime_hours": 8.76,
    "allowed_downtime_minutes": 525.6
  },
  "working": "1. Convert percentage: 99.9% / 100 = 0.999. 2. Compute unavailable fraction: 1 - 0.999 = 0.001. 3. Compute downtime: 365 days × 0.001 = 0.365 days. 4. Convert to hours: 0.365 × 24 = 8.76 hours. 5. Convert to minutes: 8.76 × 60 = 525.6 minutes."
}

Failure boundary

BREAK_CLAIMED · SELF_FLAGGED

The reverse-calculation path accepts a zero-length period mathematically presented as an input, producing an undefined division unless it rejects the input. The annual calculation also has a convention-sensitive result when the meaning of year is not specified.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche5/tranche5-results.json
• BOUNDARY_HAZARD_CATALOG.json