After connecting to an Oracle-DB PHP looses the connection because of an error on the DB-Server. The crash of oracle is not the problem, but the behaviour of our php-application: the Function Zend_Db_Statement_Oracle::_prepare() failed with an PHP-Warning ('oci_parse(): ORA-03114: not connected to ORACLE'). The coded exception was not thrown.

    protected function _prepare($sql)
    {
        $connection = $this->_adapter->getConnection();
        $this->_stmt = oci_parse($connection, $sql);
        if (!$this->_stmt) {
            /**
             * @see Zend_Db_Statement_Oracle_Exception
             */
            require_once 'Zend/Db/Statement/Oracle/Exception.php';
            throw new Zend_Db_Statement_Oracle_Exception(oci_error($connection));
        }
    }

I think the "oci_parse($connection, $sql);" needed a leading "@", so the exception can be thrown. Functions like "_bindParam" are realised with a "@".