Hope this helps. DA or DOA (double action, double action only) models when you rack the slide and chamber a round it will remain in the DA mode. DA/SA models, when you rack the slide it will draw back the hammer and it will be in SA mode. Now depending on what gun you have if you have a decocker when the decocker is engaged it will lower the hammer to DA mode or half cocked which will still be considered DA but with a shorter pull. If not a decocker you would have to carefully decock the hammer manually to lower into DA mode or leave it "cocked and locked" and engage the safety which will have it remain in SA mode. It would help to know which handgun you have or are thinking of getting to better give advice or to answer your question.