In the OfflineFeatureEditingSample, the syncGeodatabase method is called from the main thread (IBAction from Storyboard).
In our app, we have a fairly large dataset to sync (12 tables with some 100k´s of features), and we see that, as the size of the dataset increase, the UI blocks for longer periods of time. At this point, the call seem to block about 15 seconds. This is a critical issue for us, as the app triggers sync at regular intervals. With smaller datasets, this has not been an issue with the current code.
We´ve tried posting the operation on a background thread (dispatch_async/performSelectorInBackgorund), but then the we do not get status or completion callbacks.