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The SDK will continue to collect new records in the background (as long as the app isn’t swiped away). However, it cannot continuously upload while in the background. The app gets about 30 seconds of background time to upload after being backgrounded. After that, the rest of the queue must wait until the app is in the foreground again. A couple queued records might get uploaded every time a new record is received in the background, but if there is a large queue it will not be fully processed until the app is foregrounded. Also, the phone must be unlocked. No data will be uploaded while the phone is locked.
Bringing the app back to the foreground does not immediately restart the queue processing. You may want to put [[VLDSession sharedInstance] processQueue]; in the AppDelegate's -applicationDidBecomeActive method, which would ensure that as soon as the app is foregrounded, uploads are resumed.
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