Re: direct read is much faster than scattered read, is it reasonable?
Date: Wed, 28 May 2008 16:23:22 -0400
Did you mean that operations like FTS/IFFS can result in "scattered read" as well as "direct path read"? That is true and stats will be logged against relative operation.
On Wed, May 28, 2008 at 3:52 PM, Zhu,Chao <zhuchao_at_gmail.com> wrote:
> 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>
>> 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,
> Zhu Chao
-- Alex Fatkulin, The Pythian Group, http://www.pythian.com/blogs/author/alexf -- http://www.freelists.org/webpage/oracle-lReceived on Wed May 28 2008 - 15:23:22 CDT