Re: db_file_multiblock_read_count and 10g
- From: Greg Rahn <greg@xxxxxxxxxxxxxxxxxx>
- To: dbvision@xxxxxxxxxxxx
- Date: Sat, 24 Jan 2009 23:40:36 -0800
10gR2 introduced Self-Tuning Multiblock Read Count
http://download.oracle.com/docs/cd/B19306_01/server.102/b14214/chapter1.htm#FEATURENO05506
The basic premise is to allow large I/Os for MBRC operations w/o
giving the Optimizer too much preference to FTS. By default it uses a
MBRC of 8 for costing, or the system stats MBRC if it is set.
On Sat, Jan 24, 2009 at 4:18 PM, Nuno Souto <dbvision@xxxxxxxxxxxx> wrote:
> 조동욱 wrote,on my timestamp of 25/01/2009 1:44 AM:
>>
>> This is called autotuned MBRC - literally, Oracle autotunes the value of
>> MBRC.
>
>
> I don't think this is the case in 10g. Maybe in 11, but not 10gr2.
> See this:
> http://download.oracle.com/docs/cd/B19306_01/server.102/b14237/initparams047.htm#CHDFAFHE
> There is a world of difference between a "default value" and "auto-tune".
> Nowhere in that doco is it said it is auto-tuned. I do recall reading
> something from Jonathan about it being so in 11g but I won't be using 11g
> anytime soon so I can't say for sure.
--
Regards,
Greg Rahn
http://structureddata.org
--
//www.freelists.org/webpage/oracle-l
Other related posts:
