From Ryan Faas's article Apple's OpenDirectory does support overlays but I can't seem to enable the syncprov or accesslog overlays. Adding following block to slapd_macosxserver.conf turns the server in to vegetable.
# defines replica provider for this database
overlay syncprov
# contextCSN saved to database every 1000 updates or 60 minutes
syncprov-checkpoint 1000 60
What am I missing here?