The values NOTIFY, CHANGED, CLEAR and DELETE are often seen in the .audit file and the Audit Log tab on notification properties or in debug log files.
NL_NOTIFY - is logged when a new event is received from an underlying domain manager.
NL_CHANGED - is not logged by default but used when an existing notification has a state change, for example from IsRoot true to false.
NL_CLEAR - is logged when an event is cleared from the SAM server as a result of a clear from an underlaying domain manager.
NL_DELETE - is not logged by default but used when a notification is archived from a notification list.