Database limits
A refresh scheduled for a future date is evaluated a second time forty-eight hours before the scheduled launch time to ensure no issues emerged after the first evaluation. The refresh is then evaluated a third time immediately prior to the launch. If you schedule a refresh to launch immediately, then there is only one evaluation.
When a refresh is scheduled for a future date and the corresponding DB Limits check is successful, then the capacity required for the refresh is reserved on the database server. If another organization attempts to schedule a refresh for the same server, then their refresh will only pass the DB Limits evaluation if the server has enough capacity. If a scheduled refresh is canceled, then the space which was reserved for that refresh is no longer considered when future DB Limits checks are performed.