Does importing historical data overwrite existing?

[Jellybean]

Hi

If I import new historical data covering a period that overlaps existing historical data, does the imported data overwrite the existing data?

Cheers
Tony

[NinjaTrader_Kyle]

Hi Tony,

Thank you for your post.

Yes, the imported data would overwrite existing data from the same period.

[Jellybean]

Hi

I would like to download new historical data from my data provider (or NT server), but I would like to leave any previously imported data that is earlier than the period available for download. If I "reload all historical data", will earlier data remain?

For example, I have imported 1 minute data for ES ##-## covering Sep 1997 to Mar 2013, but it is not back adjusted, which I prefer. If historical data is available from Jan 2011 to today, what data will remain after I reload all historical data?

I would like my old data from Sep 1997 to Dec 2010 plus new data from Jan 2011 to today.

Cheers
Tony

[NinjaTrader_JC]

Hello Tony,

If you "Reload All Historical Data" NinjaTrader will try to download all the Historical Data from the Data Provider that you are connected to and overwrite it. You may want to use the Historical Data Manager to download the specific days of data that you would like to download from your data provider and then disconnect from the data provider so that your data is not overwritten.

http://www.ninjatrader.com/support/helpGuides/nt7/historical_data_manager.htm

[Jellybean]

Thanks JC

Not sure that answers my question, but I tried it and noted the files dates in the database.

The answer for others reading is that only data within the period being downloaded is overwritten. All other data remains.

Cheers
Tony