#DDC-2664 Document new Proxy factory flags usage as of DCOM-210

[Document new Proxy factory flags usage as of DCOM-210](http://www.doctrine-project.org/jira/browse/DDC-2664)

docs/en/reference/advanced-configuration.rst

@@ -329,24 +329,51 @@ controls this behavior is:
 .. code-block:: php
 
     <?php
-    $config->setAutoGenerateProxyClasses($bool);
-    $config->getAutoGenerateProxyClasses();
+    $config->setAutoGenerateProxyClasses($mode);
 
-The default value is ``TRUE`` for convenient development. However,
-this setting is not optimal for performance and therefore not
-recommended for a production environment. To eliminate the overhead
-of proxy class generation during runtime, set this configuration
-option to ``FALSE``. When you do this in a development environment,
-note that you may get class/file not found errors if certain proxy
-classes are not available or failing lazy-loads if new methods were
-added to the entity class that are not yet in the proxy class. In
-such a case, simply use the Doctrine Console to (re)generate the
-proxy classes like so:
+Possible values are:
+
+-  ``Doctrine\Common\Proxy\AbstractProxyFactory::AUTOGENERATE_NEVER``
+
+Never autogenerate a proxy and rely that it was generated by some
+process before deployment.
+
+To generate the proxies, use:
 
 .. code-block:: php
 
+When you do this in a development environment,
+note that you may get class/file not found errors if certain proxy
+classes are not available or failing lazy-loads if new methods were
+added to the entity class that are not yet in the proxy class.
+In such a case, simply use the Doctrine Console to (re)generate the
+proxy classes.
+
     $ ./doctrine orm:generate-proxies
 
+-  ``Doctrine\Common\Proxy\AbstractProxyFactory::AUTOGENERATE_ALWAYS``
+
+Always generates a new proxy in every request.
+
+-  ``Doctrine\Common\Proxy\AbstractProxyFactory::AUTOGENERATE_FILE_NOT_EXISTS``
+
+Autogenerate the proxy class when the proxy file does not exist.
+This strategy causes a file exists call whenever any proxy is
+used the first time in a request.
+
+-  ``Doctrine\Common\Proxy\AbstractProxyFactory::AUTOGENERATE_EVAL``
+
+Generate the proxy classes using eval(), which avoids writing the
+proxies to disk. This strategy is only sane for development.
+
+In a production environment, it is highly recommended to use
+AUTOGENERATE_NEVER to allow for optimal performances. The other
+options are interesting in development environment.
+
+Before v2.4, ``setAutoGenerateProxyClasses`` would accept a boolean
+value. This is still possible, ``FALSE`` being equivalent to
+AUTOGENERATE_NEVER and ``TRUE`` to AUTOGENERATE_ALWAYS.
+
 Autoloading Proxies
 -------------------