Enable this option if your groups are stored as standalone records in LDAP.
Example:
dn: cn=languagestudents,ou=groups,dc=mahara,dc=org objectClass: groupOfUniqueNames cn: languagestudents uniqueMember: uid=user1,dc=mahara,dc=org uniqueMember: uid=user2,dc=mahara,dc=org uniqueMember: cn=frenchclass,ou=groups,dc=mahara,dc=org