From ca64985a431d68072dc23d26394d8019a000e7a8 Mon Sep 17 00:00:00 2001
From: Michael Stack <stack@apache.org>
Date: Wed, 24 Aug 2011 06:54:38 +0000
Subject: [PATCH] HBASE-4242 Add documentation for HBASE-4071

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1160988 13f79535-47bb-0310-9956-ffa450edef68
---
 CHANGES.txt         |  1 +
 src/docbkx/book.xml | 15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/CHANGES.txt b/CHANGES.txt
index 9e8b76dc8fb..abec2806a3e 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -456,6 +456,7 @@ Release 0.91.0 - Unreleased
                (todd)
    HBASE-4071  Data GC: Remove all versions > TTL EXCEPT the last
                written version (Lars Hofhansl)
+   HBASE-4242  Add documentation for HBASE-4071 (Lars Hofhansl)
 
 Release 0.90.5 - Unreleased
 
diff --git a/src/docbkx/book.xml b/src/docbkx/book.xml
index ea4d2546412..834ba068159 100644
--- a/src/docbkx/book.xml
+++ b/src/docbkx/book.xml
@@ -263,6 +263,21 @@ admin.enableTable(table);
       compactions.  The number of versions may need to be increased or decreased depending on application needs.
   </para>
   </section>
+  <section xml:id="schema.minversions">
+  <title>
+  Minimum Number of Versions
+  </title>
+  <para>Like number of row versions, the minimum number of row versions to keep is configured per column
+      family via <link xlink:href="http://hbase.apache.org/apidocs/org/apache/hadoop/hbase/HColumnDescriptor.html">HColumnDescriptor</link>.
+      The default is 0, which means the feature is disabled.
+      The minimum number of row versions parameter is used together with the time-to-live parameter and can be combined with the
+      number of row versions parameter to allow configurations such as
+      "keep the last T minutes worth of data, at most N versions, <emphasis>but keep at least M versions around</emphasis>"
+      (where M is the value for minimum number of row versions, M&lt;=N).
+      This parameter should only be set when time-to-live is enabled for a column family and must be less or equal to the 
+      number of row versions.
+  </para>
+  </section>
   <section xml:id="changing.rowkeys">
   <title>
   Immutability of Rowkeys