Doctrine_Connection supports attributes and options, where attributes are processed after opening the connection and options may or may not be used before or after opening the connection. Attribute ATTR_PERSISTENT in particular should, in the case of a PDO connection, be specified as fourth option in the PDO constructor to let PDO really use a persistent connection. This is currently not the case. Instead of applying a special workaround for handling this persistent attribute, sfDoctrinePlugin should support separate attributes and options to be applied before- or after opening a connection. Also for Symfony users it is preferred to locate these settings in a database.yml rather than a doctrine.yml.

For more information please see doctrine-user thread  http://groups.google.com/group/doctrine-user/t/19700db17bfe5470 .