Do not understand defaultWriteConcernSource/defaultReadConcernSource

for default r/w concern ,there are two parameters:defaultReadConcern/defaultWriteConcern.
then what is the purpose of parameters:defaultWriteConcernSource/defaultReadConcernSource?
what implicit meas?

after i run admincommand to set default r/w concern, it changes to “global”.
how does implict / global influence mongo replication set?

Hi @Yi_deng and welcome to MongoDB community forums!!

As mention in the SERVER-55702- Update ‘defaultRWConcern’ section of serverStatus, it mentions the source of the default read and write concern.

This values helps in setting up the default read and write concern values by evaluating the source of the two values. This default is safe as the system shouldn’t accept writes needing a specific write concern before we have loaded our config. This prevents overriding the default write concern and its source on mongos if it has already been set through the config server.

Please reach out feel free to reach out if you have any further concerns.