public function enableCmdlCaching($duration = null)
    {
        if ($duration == null) {
            $duration = $this->duration;
        }
        $this->cmdlCaching = $duration;

        $checkLastModifiedDate = false;
        if ($this->hasLastModifiedCacheStrategy()) {
            $checkLastModifiedDate = true;
        }

        $this->readConnection->enableCMDLCaching($duration, $checkLastModifiedDate);
        if ($this->writeConnection) {
            $this->writeConnection->enableCMDLCaching($duration, $checkLastModifiedDate);
        }
    }