Cross link:
[SOLVED] Large number of slapd connections (ignore the misleading title)
Short directions-
If you want it 5.0.5 & prior style:
zmlocalconfig -e ldap_log_level=32768
zmcontrol stop/start
To set back to the new 5.0.6 style:
zmlocalconfig -e ldap_log_level=16640
zmcontrol stop/start