title: What is the difference between the different BerkeleyDB versions, and which should I choose?
body: <p>Many things depend on BDB. When I go to install the prepackaged software for my server, each piece of software seems to want a different version of BerkeleyDB.  But it seems when I compile them I can specify a specific BDB version.  (The software involved includes Postfix, OpenLDAP, and Cyrus IMAP.)</p>
  
  <p>I use BDB in python projects occaisionally and I have no clue what impact the different versions have on the database file created. </p>
  
  <p>I would like to know the difference between all the different Berkeley DB versions. It seems difficult to find information about the different versions and any API or file format differences, incompatibilities between versions, et cetera.</p>
  
  <p>I know at minimum the following versions exist:</p>
  
  <ul>
  <li><p>1.85 (a historical version?)</p></li>
  <li><p>2.x </p></li>
  <li><p>3.x </p></li>
  <li><p>4.1</p></li>
  <li><p>4.2</p></li>
  <li><p>4.3 </p></li>
  <li><p>4.4</p></li>
  <li><p>4.5</p></li>
  <li><p>4.6</p></li>
  <li><p>4.7</p></li>
  <li><p>4.8</p></li>
  <li><p>5.0</p></li>
  </ul>