Live Data, RTD, and Recalculation
Summary
Live Runline formulas use Excel RTD updates to enter the calculation graph when data changes outside the workbook.
Core Idea
An RTD-backed cell can change without a user editing the workbook. Dependent formulas then recalculate according to Excel's calculation settings and the workbook's dependency graph.
How It Works
U.SUBSCRIBE registers for report updates and returns an RTD value. Status functions such as connection state can also be RTD-backed. U.RTD_THROTTLE_MILLIS controls update pacing; it does not replace workbook calculation dependencies.
Why It Matters
Diagnosing a stale value requires identifying whether the cell is live RTD output, a direct calculation, a cached value, or a value previously pasted into a range.
In Excel (Runline U)
Keep the RTD registration cell separate from expensive transforms. Reference it from U.GET, U.DO, or downstream formulas so the external update has a visible route through the workbook.
Common Patterns
- One subscription cell drives a separate retrieval range.
- Throttle the narrowest update layer that is producing excess work.
- Use explicit trigger cells for side-effecting operations.
Misconceptions
- A successful subscription does not guarantee every dependent formula has recalculated.
- RTD throttling and publish throttling control different parts of the update path.