I have downloaded intra-day hourly bars from Interactive Brokers TWS into Amibroker for the Nasdaq100 index NDX-NASDAQ-IND-USD. The first bar started in 21June2018. I did a backfill a few minutes ago. After backfill, I noticed that the first bar data in 21June2018 is gone and my first bar now starts in 22June2018. Is it normal for backfill to delete the oldest data? Can I get Amibroker to store old historical data after backfill?
@thankyou18 check this document and some related topics:
- Database Settings
- EOD database reduction (in such a case disable the option)
- Amibroker database configuration for erasing older data (you may need to enlarge the number of bars in your DB intraday settings)
- How to increase max. number of bars (Database settings)
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@beppe, thank you very much for your helpful replies. I discovered the problem from the links you gave. Under preferences->data, the max number of saved quotations was set at 300. After I set it to a large number 10000, the problem is solved!
@thankyou18, good to hear.
I hope that my answer can encourage you to spend more time looking for answers in the forum, before posting any new request. 
As you have seen, many issues are quite common and frequently have already been addressed and resolved before.
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I posted too fast. The problem is not solved yet. Now, I get gaps in the data downloaded. Let me explore further.