I know it is strange to have Overview in the Overview, but I need to give you some details :) Generally there are 2 things which you need to care if you want to resume normal operation:

1. Restore the data
2. Make it consistent to a point of time

Simply bringing the data, usually doesn't work, because some of the data can be consistent to 1 day ago and other 1 hour ago. Imagine you have a BIIIIIG database (couple exa-bytes), do you think that if you do a full backup, the RMAN will just take a snapshot of the data as it is at that moment. NO, it will go block-by-block and that TAKES TIME, time through which that data can change. So if a block is backed up at 08:00 AM other can be backed up at 10:00 AM, you seriously thing that the data in these blocks won't have changed :) ? Well to fill that GAP we have archive log files (if they are enabled), to make our data consistent.

In the next couple pages chapters we will describe each possible scenario but here is a brief summarization of all scenarios: