{
  "slug": "rate-of-occurrence-of-failures",
  "term": "Rate of occurrence of failures",
  "aliases": [
    "ROCOF",
    "Repair rate"
  ],
  "definition": "The rate of occurrence of failures (ROCOF) is the derivative with respect to time of the expected cumulative failure count of a repairable system.",
  "note": "With N(t) the recurring failure count, M(t) = E[N(t)] and ROCOF m(t) = dM(t)/dt. The clock runs from the system's starting point; it does not restart at every event. Despite the name repair rate, this measures event frequency, not repair speed or duration. Specify the system boundary and clock; device lifetime hazard conditions on survival and is a different quantity.",
  "related": [
    "interarrival-time",
    "hazard-rate",
    "mtbf"
  ],
  "citations": [
    {
      "id": "nist-rocof",
      "title": "NIST e-Handbook 8.1.2.5: Repair rate or ROCOF",
      "url": "https://www.itl.nist.gov/div898/handbook/apr/section1/apr125.htm",
      "accessed": "2026-10-12"
    },
    {
      "id": "nist-hazard",
      "title": "NIST e-Handbook 8.1.2.3: Failure (or hazard) rate",
      "url": "https://www.itl.nist.gov/div898/handbook/apr/section1/apr123.htm",
      "accessed": "2026-10-12"
    },
    {
      "id": "hesela-measurement-clocks",
      "title": "Hesela: Disk replacement rates are not disk lifetimes",
      "url": "https://hesela.com/analyses/mttf-vs-field-replacement-rates/",
      "accessed": "2026-10-12"
    }
  ],
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-12"
}