The system has a limited amount of storage space and you are expected to download the survey data you have collected on a routine basis, and then delete it from the system. By going to View Survey Data Usage, you can see how much database space is being used. You can then download the survey data (a link is provided), and delete it from the system.
When you delete the data from the system, all survey data collected within the last 5 minutes will not be deleted, as a precaution. This is to ensure that you have had adequate time to download the survey data before deleting it (to account for the time between downloading the data and deleting it).
If you choose to delete the survey data in this manner, the record of participant sign-ups will be retained. That way you can ensure the participant does not complete the same online survey again.