“ Is the violation of the oath considered a criminal violation?”
No.
Since all the people who take the oaths are also all the people who write, enforce, and interpret the laws, the idea that the oath they take should be enforceable and their violation of said oaths subject to criminal sanction seems to have slipped to the bottom of the pile of legislative priorities.
Mencken had a few thoughts on this subject but no one has taken up their intellectual development since him. Perhaps it’s time someone did.