 In this case, the distributed transaction
         manager must send <span class="emphasis"><em>prepare</em></span> messages to each local
         manager.  The local manager must then issue a <code class="methodname">DbTxn::prepare()</code> and
         await its successful return before responding to the distributed
         transaction manager.  Only after the distributed transaction manager
         receives successful responses from all of its
         <span class="emphasis"><em>prepare</em></span> m