Re: AIX Concurrent I/O for Oracle archive logs

  • From: Subodh Deshpande <deshpande.subodh@xxxxxxxxx>
  • To: Brandon.Allen@xxxxxxxxxxx
  • Date: Tue, 25 May 2010 23:50:34 +0530

Hi Allen,

I think the document discusses about the block size of OS and block size of
database as well. If OS block size is greater than oracle db block size then
it should not be a problem I suppose. If it is revers is the case then it is
going give performance problem.
OS block size should be multiple of oracle db block size while installing db
usually I keep this ratio as 1:2 i.e. if my os block size is 4096 then my
oracle block size will be 2048. If I am going to use dbnk parameter then I
will have to think of my os block size so that none of the table space
having different bloxk size and hence performance will not get affected..use
of dbnk parameter is again a purely related to architecture and nature of
application being used.

in your case what is going to be control file, redo, archive log size for
which you want to use DIO/CIO.

On 25 May 2010 21:36, Allen, Brandon <Brandon.Allen@xxxxxxxxxxx> wrote:

>  Hi List,
> Can anyone think of a good reason why Oracle’s archived redo logs shouldn’t
> be placed on a non-buffered (concurrent or direct IO) file system?  Oracle
> Support document 418714.1 specifically states NOT to use DIO/CIO for file
> systems containing archive logs.    However, I have one AIX system where my
> archive logs have been on a file system mounted with CIO for years and I’ve
> never had any problems (and yes, I’ve successfully used the logs for actual
> recovery).
> I’m considering moving another of my systems to CIO because on the other
> system, when archive log backups run, the AIX file system cache gets flooded
> by the archive logs and it has recently started causing the OS to start
> paging heavily, which in turn is bringing the system to a screeching halt
> for a few minutes, so I think if I move the logs to a CIO file system then
> they should no longer be read into the AIX buffer cache, and that should
> prevent this problem, but I just want to see if anyone has any good reasons
> why I should avoid using CIO with archive logs.
> Thanks,
> Brandon
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