No it is not normal, when did the spots appear?
Other members are asking the questions above as it can help to diagnose what the problem is. Tank size, filtration, how long the tank has been cycled and most importantly tank water stats for ammonia, nitrIte and less importantly nitrAte and ph can all help in finding out why the spots have appeared.
Without knowing those, I would only guess at ammonia burns, which can appear as black spots/marks on the fish skin.
Help us to help you and give the information so we can help your Oscar and you