Add back-hdb description

doc/man/man5/slapd-bdb.5

@@ -3,7 +3,7 @@
 .\" Copying restrictions apply.  See COPYRIGHT/LICENSE.
 .\" $OpenLDAP$
 .SH NAME
-slapd-bdb \- BDB backend to slapd
+slapd-bdb, slapd-hdb \- BDB backends to slapd
 .SH SYNOPSIS
 ETCDIR/slapd.conf
 .SH DESCRIPTION
@@ -15,6 +15,10 @@ it properly.
 It uses the Sleepycat Berkeley DB (BDB) package to store data.
 It makes extensive use of indexing and caching to speed data access.
 .LP
+"hdb" is a variant of the BDB backend that uses a hierarchical database
+layout which supports subtree renames. It is otherwise identical to
+the "bdb" behavior, and all the same configuration options apply.
+.LP
 It is noted that these options are intended to complement
 Berkeley DB configuration options set in the environment's
 .B DB_CONFIG
@@ -28,14 +32,14 @@ take precedence.
 These
 .B slapd.conf
 options apply to the BDB backend database.
-That is, they must follow a "database bdb" line and come before any
-subsequent "backend" or "database" lines.
+That is, they must follow a "database bdb" or "database hdb" line and
+come before any subsequent "backend" or "database" lines.
 Other database options are described in the
 .BR slapd.conf (5)
 manual page.
 .TP
 .B cachesize <integer>
-Specify the size in entries of the in-memory cache maintained 
+Specify the size in entries of the in-memory entry cache maintained 
 by the BDB backend database instance.
 The default is 1000 entries.
 .TP
@@ -76,7 +80,9 @@ will return a different result.
 .B idlcachesize <integer>
 Specify the size of the in-memory index cache, in index slots. The
 default is zero. A larger value will speed up frequent searches of
-indexed entries.
+indexed entries. An hdb database needs a large idlcachesize
+for good search performance, typically three times the entry cache size
+or larger.
 .TP
 .B
 index {<attrlist>|default} [pres,eq,approx,sub,<special>]

doc/man/man5/slapd-bdb.5.links

+slapd-hdb.5