I have compiled OpenLDAP 2.4.16 from source by using following command
*CC=gcc CPPFLAGS=-I/usr/local/BerkeleyDB.4.7/include
LDFLAGS=-L/usr/local/BerkeleyDB.4.7/lib
LD_LIBRARY_PATH=/usr/local/BerkeleyDB.4.7/lib ./configure --enable-bdb
--enable-hdb --with-cyrus-sasl --with-tls --enable-ldap --enable-overlays
*
After that I configure slapd.conf to load denyop overlay module but
slapd can not load it .I have not seen any file name denyop or similar
one in file sysem.Where is a path of openldap overlay moudules?