Glossary term
Degraded run
Definition
A snapshot too old, or a source offline, labeled Cached — not Live. Fluent notes on a stale tape are stories. No paper records on a degraded run.
How it works
A degraded run is a run whose inputs were not good enough for its outputs to be trusted: a snapshot too old, or a source offline. The status is labeled Cached rather than Live, and the process stops instead of filling gaps. No paper records are made on a degraded run, because anything written would look as authoritative as a real reading.
Staleness has a size that can be computed. Price uncertainty grows with the square root of time, so the plausible band around a quote of age t is price × volatility × √(t / 98,280), where 98,280 is the number of minutes in a 252-day trading year of 390-minute days. Inverting the formula gives the oldest a quote may be for a stated tolerance.
Worked example
Take a hypothetical index-tracker quote of $500 with 16% assumed volatility that is 70 minutes old. The band is 500 × 0.16 × √(70 / 98,280) = 500 × 0.16 × 0.0267 = about $2.14, or 0.43% of price.
To keep the error within ±0.25%, the allowed age is 98,280 × (0.0025 / 0.16)² = about 24 minutes. A volatile single name at 60% volatility would need its quote under 2 minutes old for the same tolerance. One global freshness setting cannot be right for both, which is why the course derives thresholds instead of choosing one.
Hypothetical, for education only. Not a recommendation and not a prediction.
Common mistake
The mistake is judging a note by how fluent it is. Prose does not know how old its inputs were, so a confident paragraph on a stale tape is a story, not a reading. A related error is interpolation, filling in the missing print so the page looks finished. A stopped process leaves an honest hole; a completed one on invented values leaves an artifact with no record of which parts were real.