Re: Re: Automatic tuning of db_file_multiblock_read_count ???

Jared,  

it seems the theme I was looking for isn't yet published on that site - it might be in the upcoming Part 3.  

But I have found some stuff in the docs, Perf. Tuning Guide, 14.4:  

"In release 10.2, the optimizer uses the value of mbrc when performing full table scans (FTS). The value of db_file_multiblock_read_count is set to the maximum allowed by the operating system by default. However, the optimizer uses mbrc=8 for costing. The "real" mbrc is actually somewhere in between since serial multiblock read requests are processed by the buffer cache and split in two or more requests if some blocks are already pinned in the buffer cache, or when the segment size is smaller than the read size. The mbrc value gathered as part of workload statistics is thus useful for FTS estimation."  

Peter  

Jared Still <jkstill_at_gmail.com> wrote:The articles by Arup Nanda contain a bit more detail on this:

http://www.oracle.com/technology/pub/articles/10gdba/index_r2.html

Jared

On 7/13/05, Peter Alteheld <palteheld_at_yahoo.de> wrote:In a future breaking news (from August 2nd,2005 ;-) Don Burleson lists this as a performance improvement in 10g R2 - see:  

http://dba-oracle.com/oracle_news/2005_8_2_10gr2_performance.htm  

I haven't found anything about that in the docs. Has anyone out here more info about it?

-- 
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist 



		
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