Originally posted by jlakhani
so what you are really saying is that by over allocating more channels, I can actually slow down the rman restore? howz that possible? can somebody explain me that?
They will compete for bandwidth. Can you answer some of my questions? Were all the channels used in the restore? Do you have that many tape devices? Was anything else being done on the tape system at the same time?

You need to benchmark backups with different channels... take the size of the backup file divide by the time it took to back up. Do this for each piece that is backed up (i.e channel). Sum it up for all the pieces. You will get your throughput and you can see what is optimal. You may get 10M a minute with 2 channels, but only get 7M a minute with 3 channels, etc. I'd use the same for restore that I used to back up. How many do you use on your daily backups that take 3 hours?

Also, a restore WILL take longer than a backup... and depending on how many archive logs you have to restore, that will add time too. But it shouldn't be 4x.

Lastly, there could be a problem with your tape system. I have had to do a few restores here, and every once in a while, I will watch how much data is coming across, and I'll get like 30 MEG in 1 hour. It's weird. I stop and start the restore, and it flies. Nobody here knows why, and I know how to fix it, so if I see it I just stop it and start over. So I would watch the restore rate to see if you have some problem there too.

HTH
Jodie