From ae1c361f797a104a35aef967cc694b457217f488 Mon Sep 17 00:00:00 2001
From: Siri Hansen <siri@erlang.org>
Date: Thu, 3 Nov 2011 15:01:11 +0100
Subject: Add documentation for upgrade from pre R15 to post R15 sasl

---
 system/doc/design_principles/appup_cookbook.xml | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

(limited to 'system')

diff --git a/system/doc/design_principles/appup_cookbook.xml b/system/doc/design_principles/appup_cookbook.xml
index eebe6ba7b4..798b23d847 100644
--- a/system/doc/design_principles/appup_cookbook.xml
+++ b/system/doc/design_principles/appup_cookbook.xml
@@ -640,5 +640,23 @@ code_change(_OldVsn, State, port) ->
       updates etc. can be used without having to specify <c>.appup</c>
       files.</p>
   </section>
+
+  <section>
+    <title>Emulator Upgrade from pre OTP R15</title>
+    <p>From OTP R15, an emulator upgrade is performed by restarting
+    the emulator with new versions of the core applications
+    (<c>kernel</c>, <c>stdlib</c> and <c>sasl</c>) before loading code
+    and running upgrade instruction for other applications. For this
+    to work, the release to upgrade from must includes OTP R15 or
+    later. For the case where the release to upgrade from includes an
+    earlier emulator version, <c>systools:make_relup</c> will create a
+    backwards compatible relup file. This means that all upgrade
+    instructions will be executed before the emulator is
+    restarted. The new application code will therefore be loaded into
+    the old emulator. If the new code is compiled with the new
+    emulator, there might be cases where the beam format has changed
+    and beam files can not be loaded. To overcome this problem, the
+    new code should be compiled with the old emulator.</p>
+  </section>
 </chapter>
 
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