Database limits
For certain applications, after a refresh is scheduled, the request is evaluated. This step is known as DB Limits, and it evaluates the refresh request for potential issues that can cause the refresh to fail. If any issues are identified during the DB Limits evaluation, the refresh is canceled, and you receive a notification.
The refresh is evaluated a second time shortly before the scheduled launch time to ensure no issues emerged after the first evaluation. If you schedule a refresh to launch immediately, then there is only one evaluation.