I think the core schema is in use as it is in the /etc/ldap/slapd.d /cn=config cn=config.ldif
/etc/ldap/slapd.d/cn=config cn=module{0}.ldif cn=schema.ldif olcDatabase={-1}frontend.ldif olcDatabase={0}config.ldif olcDatabase={1}mdb.ldif
/etc/ldap/slapd.d/cn=config/cn=schema cn={0}core.ldif cn={1}cosine.ldif cn={2}nis.ldif cn={3}inetorgperson.ldif
Thanks Bob H