Re: 10g RAC and db_multi_block_read_count
- From: Greg Rahn <greg@xxxxxxxxxxxxxxxxxx>
- To: Jon.Crisler@xxxxxxx
- Date: Wed, 5 Aug 2009 09:08:33 -0700
Could you cite the reference that you mentioned about the MBRC=8 on
RAC suggestion?
What is your workload? DSS? OLTP?
Given that not setting db_multi_block_read_count basically results in
a costing of 8 w/o system stats but I/O size is
db_multi_block_read_count blocks or in this case 1MB.
I look at it like this: is it more efficient to execute a larger
number of smaller I/Os or a smaller number of larger I/Os when doing a
FTS operation (the answer is the latter)? Then I would ask myself,
does it even make any difference if it is RAC or not, and if so, why?
I am struggling to think of any significant difference that RAC would
introduce, so I would comment that it makes no difference and if the
comments you found have no technical explanation, I would classify it
as mis-information.
On Wed, Aug 5, 2009 at 8:28 AM, Crisler, Jon<Jon.Crisler@xxxxxxx> wrote:
> If I allow Oracle 10g to automatically set the parameter
> db_multi_block_read_count, the value is determined to be 128 (8k
> blocksize). However, I ran across some comments that suggest in a RAC
> environment that this large size might be a bad choice, and it should be
> backed down to 8. I cannot find any info in statspack / AWR that
> suggests a smaller number is better in RAC.
>
> Does anybody have further insight into this value in a RAC environment ?
--
Regards,
Greg Rahn
http://structureddata.org
--
//www.freelists.org/webpage/oracle-l
Other related posts:
