Re: USING COST BASED OPTIMISATION ON A MULTI-PROCESSOR,MULTI-DISK DRIVE SERVER

Home -> Community -> Usenet -> c.d.o.server -> Re: USING COST BASED OPTIMISATION ON A MULTI-PROCESSOR,MULTI-DISK DRIVE SERVER

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Thu, 18 Mar 1999 22:28:03 -0000
Message-ID: <921796289.10891.1.nnrp-09.9e984b29@news.demon.co.uk>

A nice feature in 8.0.5 though (possibly 8.0.4) is that you can introduce a weighting on how likely it is for index blocks to be buffered. This makes it much more likely for Oracle to choose an index-driven path, and is 'more appropriate' according to the readme.doc than the trick of setting FIRST_ROWS optimisation.

Can't remember the name of the init.ora parameter at present, sorry.

Jonathan Lewis
Yet another Oracle-related web site: www.jlcomp.demon.co.uk

keith boulton wrote in message <36ef7d08.1495630_at_195.147.246.90>...
>At the risk of appearing obsessed about it - my experience is that the
>cost based optimiser far too often chooses full tables scans and hash
>joins. The solution to this is to set optimizer_mode=first_rows in
>init.ora. This can be overridden with hints on a case by case basis if
>required.
>
Received on Thu Mar 18 1999 - 16:28:03 CST