Hi Ramanjaneyulu,
many thanks for your answer! 
Taking a look within RSA7 shows the corresponding data source but with "0" in column "Total":
The "time safetyinterval" of 2 to 3 hours should not be the problem. Delta records should now be available (The extraction runs on our test system every 15 minuten) but there are no delta records:
Like you can see on the first given picture of this thread new records in FULL mode are extracted between 4:30 and 4:45 AM. That means that this records should now be already available within delta mode but there are no new records:
