nextcloud/settings/ajax/setbackgroundjobsmode.php

<?php
/**
* ownCloud
*
* @author Jakob Sack
* @copyright 2012 Jakob Sack owncloud@jakobsack.de
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
* License as published by the Free Software Foundation; either
* version 3 of the License, or any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU AFFERO GENERAL PUBLIC LICENSE for more details.
*
* You should have received a copy of the GNU Affero General Public
* License along with this library.  If not, see <http://www.gnu.org/licenses/>.
*
*/

// Init owncloud
require_once('../../lib/base.php');

OC_Util::checkAdminUser();
OCP\JSON::callCheck();

$mode = isset( $_POST['mode'] ) ? $_POST['mode'] : '';
if( $mode == "none" || $mode == "ajax" || $mode == "webcron" || $mode == "cron" ){
	OC_Appconfig::setValue( 'core', 'backgroundjobs_mode', $_POST['mode'] );
}

echo 'true';