Uptime / SLA Availability Calculator

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Computing & Information

Tranche

tranche-5

Evidence ID

t5-048

Ledger rows

1

No ledger note is attached.

Review findings

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.

Formula and scope findings

• 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.

Unit assumptions

• 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.

Boundary hardening

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.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "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."
}

Related workflows

Sources and evidence

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

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