For an explanation on how background sync works, starting with iOS 7, please read this article here.
Article ID: 645
Created On: Mon, Sep 22, 2014 at 12:05 PM
Last Updated On: Mon, Sep 22, 2014 at 12:05 PM
Online URL: https://www.2doapp.com/kb/article/how-often-does-2do-sync-in-the-background.html