From efe7294639b84e668a43d467adf92d04ac95023d Mon Sep 17 00:00:00 2001
From: Marcin Siodelski <marcin@isc.org>
Date: Wed, 11 Mar 2015 21:17:09 +0100
Subject: [PATCH] [3673] Updated Kea guide with the limitations for the SQL
 timestamps.

---
 doc/guide/admin.xml | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/doc/guide/admin.xml b/doc/guide/admin.xml
index df48e44e8b..4de3c835c6 100644
--- a/doc/guide/admin.xml
+++ b/doc/guide/admin.xml
@@ -432,6 +432,22 @@ host    <replaceable>database-name</replaceable>    <replaceable>user-name</repl
         <!-- @todo: document PgSQL upgrade once they are implemented in kea-admin -->
       </section>
     </section> <!-- end of PostgreSQL sections -->
+    <section>
+      <title>Limitations related to the use of the SQL databases</title>
+
+      <para>
+        The lease expiration time is stored in the SQL database for each lease
+        as a timestamp value. Kea developers observed that MySQL database doesn't
+        accept timestamps beyond 2147483647 seconds (maximum signed 32-bit number)
+        from the beginning of the epoch. At the same time, some versions of PostgreSQL
+        do accept greater values but the value is altered when it is read back.
+        For this reason the lease database backends put the restriction for the
+        maximum timestamp to be stored in the database, which is equal to the
+        maximum signed 32-bit number. This effectively means that the current
+        Kea version can't store the leases which expiration time is later than
+        2147483647 seconds since the beginning of the epoch (around year 2038).
+      </para>
+    </section>
   </section> <!-- End of Database sections -->
 
 </chapter>
-- 
2.47.2