The specific steps needed to change the map depends on the name service that you are using.
Notification is required so that the users can run the automount command as superuser on their own systems, if necessary.
For example, suppose you modify the auto_direct map so that the /usr/src directory is now mounted from a different server. If /usr/src is not mounted at this time, the new entry becomes effective immediately when you try to access /usr/src. If /usr/src is mounted now, you can wait until the auto-unmounting occurs, then access the file.