I work primarily in Autocad for all of the drawings of my airport. This is because of Autocad being an industry go-to (for the most part) for all things relating to construction and mapping, or at least in my business it seems to be. So when a contractor puts in new waterlines, they give me an Autocad drawing that is geolocated. I then paste the geometry into my Autocad "base map" of the entire site.
My next step is to the bring the entire set of waterlines into ArcMap pulling the dwg file from the Catalog by using the Cad to Geodatabase tool. I can then create/view/edit my attribute table. But what happens when a year later after new construction and I use the Cad to geodatabase tool to bring in the updated waterlines cad drawing, does the new drawing overwrite/erase all of the existing geodata in ArcGIS?