Переключение между серверами DB

index.php

<?php

require_once(dirname(__FILE__) . '/protected/components/WebApplication.php');
Yii::createApplication('WebApplication', dirname(__FILE__) . '/protected/config/main.php')->run();

main.php

<?php

return array(
	// ...
	'components' => array(
		'db' => array(
			'enabled' => false
		),
		'db1' => array(
			'class' => 'CDbConnection',
			'connectionString' => 'mysql:host=localhost;dbname=XXX',
			'username' => 'XXX',
			'password' => 'XXX',
		),
		'db2' => array(
			'class' => 'CDbConnection',
			'connectionString' => 'mysql:host=localhost;dbname=XXX',
			'username' => 'XXX',
			'password' => 'XXX',
		),
	),
	// ...
);

WebApplication.php

<?php

class WebApplication extends CWebApplication {
	private $_db_component;
	public function getDb() {
		if ($this->_db_component === null) {
			try {
				$this->_db_component = 'db1';
				$db = $this->getComponent('db1');
				$db->setActive(true);
				return $db;
			} catch (Exception $e) {
				$this->_db_component = 'db2';
				return $this->getComponent('db2');
			}
		}
		return $this->getComponent($this->_db_component);
	}
}