Finding exact mismatched column name

[JobHelper]

source and target has around 400 columns and session fails due to mismatch in data type between source and target port. Can any one please let know, how to find exact mismatched column name?.Thanks for your time.

NOTE : [This question was asked by nashim]

[chakravarthy_info]

Try to debug the mapping the mapping then you can find easily the mismatched colum.