The directory server daemon, slapd, reads the current configuration when it is started. If you change the configuration while slapd is running, the updated configuration is automatically re-read by the daemon when you save the configuration.
If you make a modification to the configuration, the files in the current directory are copied to the previous directory. The files are copied only once in the course of an administrative session. This means that you have a copy of the configuration that was in effect before you made any modifications. If you forget to save the changes to the configuration file, the next time you start the Admin Console you are asked whether you want to update the configuration with previously recorded changes.
