Re: db_file_multiblock_read_count and 10g

From: Greg Rahn <greg_at_structureddata.org>
Date: Sat, 24 Jan 2009 23:40:36 -0800
Message-ID: <a9c093440901242340t6d894147sc85b91eb4f1d347b_at_mail.gmail.com>



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_at_iinet.net.au> wrote:
> 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
--
http://www.freelists.org/webpage/oracle-l
Received on Sun Jan 25 2009 - 01:40:36 CST

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