Data Conversion Transformation - Output has source columns and also converted datatyes columns

HI

Need some clarification for Data COnversion Transformation.

I have a Data COnversion transformation which has 5 input columns of unicode data type.
I change the datatypes for these columns to proper string .int datatypes .

Next When I redirect the output to OLEDB Destination,I get 10 output columns in Mappings for OLEDB Destination.
5 columns of unicode datatype from original source and 5 columns with datatypes after conversion.


I want to have only 5 columns (converted output) from the data conversion task and dont want the source unicode fields.


Is it possible? If Yes how ? :)
Also what is the performance impact if I dont remove the source columns?

Thanks in advance
Mou

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mou