When Oracle is doing instance recovery or when we are doing Media recovery, is any part of the Memory involved.
Or does oracle writes directly to the datafile or does it pass through the any part of th memory(sga). ?If so which part ?
Buffer cache is havily involved in any kind of recovery. Redo/archived logs contain change vectors and those changes must be performed on actual database blocks. That can be done only inside buffer cache and those changed blocks are then written to disks by DBWR. After all, that's why roll-forward part of recovery is also often refered to as cache recovery.
Jurij Modic ASCII a stupid question, get a stupid ANSI
24 hours in a day .... 24 beer in a case .... coincidence?
What you're asking is much too complicated to explained in a forum post. I suggest you read Oracle's documentation on Backup and Recovery for more information. You will certainly, and fairly easily, find the answer you're looking for.