Recent historical data is pulled from the stores in the local cache repository, local to each server.
Flashback
Flashback allows you to take the user interface, used for real-time monitoring, back to a point-in-time of the recent past (i.e. yesterday at 10:00, or last week at this time).
Time Slicing
Time Slicing is a report on recent history that shows top resource usage over a period of time.