see the help page https://www.amibroker.com/guide/w_dbsettings.html
says that ‘This setting has no effect if data source is set to (local)’. So, if :
Step1. File -> Import ASCII (1-minute data) to create a new symbol (100,000 bars).
Step2. Configure DDE for this new symbol, keep ‘Number of bars’ = 1000 (no change).
Step3. Database settings -> Data Source: DDE + Local data storage [v] Enable.
[v] Local data storage means ‘external data are cached in local files’,
But I think, this new symbol was saved as a normal symbol on local disk.
So, does ‘Number of bars’ still limit the file size of this new symbol (when DDE is running)?
The manual says:
this setting has no effect if DATA SOURCE is set to (local)
and it means DATA SOURCE, not any other field,
and you have set not to local but "DDE"
Database settings -> Data Source: DDE
Your database is PLUGIN DRIVEN (In your case DDE).
ANY plugin driven database is subject to "Number of bars" setting. When database is plugin driven, it uses "Number of bars" setting in File->Database Settings as the upper limit of bars per symbol.
Read carefully this: http://www.amibroker.com/guide/h_workspace.html
FWIW: the field below called "Local data storage" does NOT define data source. It only tells to store data on disk once obtained from the plugin.