Oracle's management of Flashback files

Question

Hi there
I have a db_recovery_file_dest_size=150GB which I now need to reduce by nearly half doe to SAN constraints.
In my flash recovery area 100GB is currently being used - as follows:
55GB - flashback files
40GB - backup sets
5 GB - archive logs
My flashback retention policy is 2 days.
However there are flashback files going back nearly 2 months!
So the logical place to gain disk space here is to reduce the number of flashback files being retained beyond the 2 day period I need.
Now I understand that I cannot simply delete the files as they are oracle managed.
My question is this.
If I try and reduce the db_recovery_file_dest_size to say 80GB how does oracle manage this. i.e. my new limit will be < than the space currently being used. Will oracle simply delete the unnecessary flashback files? And will oracle start to curtail the number of files being retained?
Thanks
Niall

Answer 1

[url http://docs.oracle.com/cd/E11882_01/server.112/e10897/backrest.htm#CHDEFIHF]Even after files in the fast recovery area are obsolete, they are typically not deleted until space is needed for new files. The restore point issue is mentioned in MOS Space issue in Flash Recovery Area( FRA ) [ID 829755.1], but the answer to your question seems curiously absent in the docs, not that I looked particularly hard.
I've never shrunk an FRA, so I'm also curious what will happen. I suspect you might want to manually delete some backups with the associated crosscheck and delete obsolete (or backup to elsewhere to accomplish the same thing), so you don't get into an extreme space pressure situation that kills archiving, then shrink the FRA and do some backup operation to set off cleanup operations.