diff --git a/doc/guide/admin/referrals.sdf b/doc/guide/admin/referrals.sdf
index c206b4e0d9..0a4692349b 100644
--- a/doc/guide/admin/referrals.sdf
+++ b/doc/guide/admin/referrals.sdf
@@ -139,3 +139,8 @@ installation has already been built using referrals, the use of the
 of the Directory system. A better approach would be to use explicitly
 defined local and proxy databases in {{subordinate}} configurations to
 provide a seamless view of the Distributed Directory.
+
+Note: LDAP operations, even subtree searches, normally access only one
+database. That can be changed by gluing databases together with the
+{{B:subordinate}}/{{B:olcSubordinate}} keyword. Please see {{slapd.conf}}(5) 
+and {{slapd-config}}(5).