           If a home directory is not supplied to 
                         
                        <span><code class="methodname">DbEnv::open()</code>, </span>
                        
                        then the directory identified by the <code class="literal">DB_HOME</code> environment variable
                        is used <span class="emphasis"><em>if</em></span> you specify
                            <span>
                                either the <code class="literal">DB_USE_ENVIRON</code