I did rs.addArb().
but, the following error came out.
MongoServerError: Reconfig attempted to install a config that would change the implicit default write concern. Use the setDefaultRWConcern command to set a cluster-wide write concern and try the reconfig again.
So, I searched the Internet to find out the cause of the error and found the following answers.
Based on the answer, I was able to solve the problem by changing the Default Write Concert.
However, I found a contradiction in rs.add() where no errors appear.
I think this was a contradiction because I didn’t fully understand the answer.
Can I ask for a more detailed explanation of the answer?