protected function _releaseFile($sIdent, $iLockMode = LOCK_EX)
    {
        $blSuccess = true;
        if (isset($this->_aLockedFileHandles[$iLockMode][$sIdent]) &&
            $this->_aLockedFileHandles[$iLockMode][$sIdent] !== false
        ) {
            // release the lock and close file
            $blSuccess = flock($this->_aLockedFileHandles[$iLockMode][$sIdent], LOCK_UN) &&
                         fclose($this->_aLockedFileHandles[$iLockMode][$sIdent]);
            unset($this->_aLockedFileHandles[$iLockMode][$sIdent]);
        }

        return $blSuccess;
    }