toilet flange on concrete

redoing the basement bathroom right now, and have a toilet flange that is set up so the top of it is flush with the top of the concrete... so the concrete is poured around it and leveled.. this seems to be holding it in place pretty well.. it is not screwed down in any way to the concrete... should it be screwed down with tapcon screws or is this enough to hold it? its not sitting on concrete, its embedded into the concrete