I try to install update for XCode and high sierra 10.13.2
However, there is phantom process which I cannot restart.
All the sql-developer process is gone but somehow it thinks its still there.
Super User is a question and answer site for computer enthusiasts and power users. It only takes a minute to sign up.Sign up to join this community
You can force kill the process through terminal
Then proceed to restart
To get to your original objective which I interpreted as 'restarting your macOS'.
1Forcefully killing processes can have unintended side-effects.