jcl,

For the IB plugin, the manual says this is the volume policy:


Okay, so I can download M1 volume.

Now suppose that:
* I only had the IB plugin.
* I need the M30 volume. (That is, I need all of the volume for one thirty-minute bar.)
* I need this info both in backtests and live.
* I need to use priceRecord() to update volume data live.

Therefore, I must do this:
* Download the M1 data from IB using the IB plugin with script "A".
* Convert the M1 volume to accumulated volume for consistency purposes with script "A".
* Script "B" is a separate trading script. (It must be separate, because the historical data will be modified.)
* The script has BarPeriod = 30 (or BarPeriod * Timeframe == 30).
* Calculate bar volume with my own indicator. (It just determines the difference in accumulated volume between this bar and the last bar, accounting for exceptions/resets.)
* Finally, priceRecord() will continue to add accumulated volume to the historical data.

Is my understanding correct?

Yes, that looks correct to me. I don't know why the volume is different in live data, but probably the API delivers it so.

Thanks for the clarification.

Currently, my Sierra Chart plugin automatically emulates accumulated volume for historical downloads, so that historical and live match. I am considering offering additional options.