Re: direct read is much faster than scattered read, is it reasonable?
- From: "Zhu,Chao" <zhuchao@xxxxxxxxx>
- To: afatkulin@xxxxxxxxx
- Date: Thu, 29 May 2008 03:52:52 +0800
some direct path read can caused by "scattered read" as well, like parallel
read into pga, and when "serial_direct_path_read=true"
On Thu, May 29, 2008 at 1:08 AM, Alexander Fatkulin <afatkulin@xxxxxxxxx>
wrote:
> You can take a look at v$event_histogram to see how distribution goes
>
> don't forget that direct path reads are done by 1M chunks
> (_db_file_direct_io_count) while scattered read are driven by
> db_file_multiblock_read_count -- it might as well be that your SAN is able
> to do better prefetching in case of 1M chunks, you can find out by altering
> dbfmrc at the session level to a different values and see how it will affect
> the results
>
>>
>>
>> Thanks,
>> Qihua
>>
>
>
>
> --
> Alex Fatkulin,
> The Pythian Group,
> http://www.pythian.com/blogs/author/alexf
--
Regards
Zhu Chao
www.cnoug.org
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