title: How to connect to multiple databases within Drupal
body: <p>I want to deploy <a href="http://drupal.org/project/openpublish" rel="nofollow">openpublish</a> on about 5 drupal multisite by high traffic on website and want to use multiple database server but some tables should be shared. 
  How to connect to multiple databases within Drupal by making share on 'users', 'sessions' and 'role' tables.</p>