Many years ago (oracle 6), I got called to a clients site to recover a database. Oracle had sent their "fireman of the year" consultant, and he said: "You hot backup procedures did not backup the controlfiles correctly" There is no way to recover the database (oracle 6 didn't have a "create controlfile" command). The client stood to lose 2 years of data He told them they were SOL. So they called me.
I was brand-new to Oracle at the time, and had never run it a production environment, much less done a recovery. While the "fireman of the year" was technically correct about not backing Oracle 6 controlfiles correctly in hot backups, he didn't as the client the right questions. I asked some different ones:'
"Do you have any exports of the database anywhere?"
"No"
"Do you have any backups of the system taken at any time when the database was down?"
"No"
"Are you sure? Absolutly none at all?"
"Well I did backup the system after the database crashed."
"Good. Restore the controlfiles from it. We will procede from there"
The "Fireman of the Year" did assist with the media recovery after the restore. I could have done it but I hadn't done one before and it would have taken me longer.
The thing I learned from that system operator is: Always backup everything you can after a crash. Those backups may be the ones that save your ass.