When people talk about redo log size, they always recommend making it large enough to switch every 30 minutes or 15 minutes. The reason is that if it is too small, it increase I/O load by issuing more checkpoints and push ARCH process to do more work. However, how about redo log file size too big? Suppose you got a log file of 1G and it switches twice a day. What are the risks you face here? My understanding is that if you do a shutdown abort and then bring the database up, the instance recovery time will increase significantly. But what if you make it checkpoint every 15 minutes (set log_checkpoint_timeout to 900, for example). (1) Will you experience the same amount of time during instance recovery? (2) If you lost your current log file group, did you lose 15 minutes of transactions or 1G of transactions?