Re: ReDo's on Raw Files on AIX?? Yay or Nay??

On 8 Apr 2004 18:48:43 -0700, Charles <cdavis10717_at_comcast.net> wrote:

> All,
>
> What's your opinion of putting redo's onto raw devices on AIX 5?
>
> Any hazards, drawbacks, corruption issues, management issues?
>
> I look forward to hearing your experience and opinions.
>
> Thanks.
>
> Charles

Raw is thoroughly recommended for online redo, whatever your O/S. The absence of buffered I/O is rather more important to LGWR than to DBWR. And since LGWR is, effectively, a foreground write whereas DBWR is a background write (a commit's not a commit until LGWR has flushed successfully), it becomes rather more important to your users, too.

The only drawback is the inevitable drawback with raw: no 'cp', no 'mv'. But I would suggest that redo logs are substantially less prone to such 'management' than data files in any case (once you've got the right number of logs at the right size, you tend to just leave them alone. It's not as if they need to grow dynamically or anything, like data files might need to do). Therefore, the lack of such management capabilities is no real loss at all. It might be a different matter if you haven't yet tuned your redo logs, so that you aren't quite sure whether you've got the right number of the right size: then flexibility is pretty key. But if you've already tuned your redo subsystem, heaving the lot onto raw has only got to make a good situation better.

Regards
HJR

-- 
-------------------------------------------
Dizwell Informatics: http://www.dizwell.com
  -A mine of useful Oracle information-
          -Windows Laptop Rac-
    -Oracle Installations on Linux-
===========================================