Re: direct read is much faster than scattered read, is it reasonable?
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_at_gmail.com> 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
> Alex Fatkulin,
> The Pythian Group,
-- Regards Zhu Chao www.cnoug.org -- http://www.freelists.org/webpage/oracle-lReceived on Wed May 28 2008 - 14:52:52 CDT