PUBLIC options can be set for a user, user extended role, or the PUBLIC role. They can be set for self or for another user or role.
Setting a PUBLIC option for the PUBLIC role sets the value for all users who do not already have the PUBLIC option set at the user level. Setting a PUBLIC option for a user or user-extended role overrides any value defined at the PUBLIC role level.
No system privilege is required to set a PUBLIC option for self, but does require the SET ANY PUBLIC OPTION system privilege to set for another user, user-extended role, or PUBLIC role. PUBLIC options cannot be set for user-defined roles. PUBLIC database options take effect immediately. No shut down and restart of the database server is required for the change to take effect.