Re: Hints
- From: "Tim Gorman" <tim@xxxxxxxxx>
- To: neil_chandler@xxxxxxxxxxx, ian@xxxxxxxxxxxxxxxxx
- Date: Mon, 15 Aug 2011 20:50:09 +0000
Neil,
I like the point you raise, which I tend to express as "don't burn down the
forest while trying to light your cigarette".
Thanks!
-Tim
-----Original Message-----
From: Neil Chandler [mailto:neil_chandler@xxxxxxxxxxx]
Sent: Monday, August 15, 2011 02:25 PM
To: ian@xxxxxxxxxxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Re: Hints
There are 2 problems with using optimizer_index_cost_adj. Tim covered the first
extensively (it's a problematic parameter). However, the main reason for me is
that you shouldn't use global parameters to get around a problem with a few of
sections of code. There are so many other options to control optimisation;
object stats, histograms, system stats, hints, outlines, profiles and baselines
to name a few. as well as rewriting the code of course. Try not to use the
sledgehammer of global change unless you have global problems and will see an
overall net benefit from such an implementation. RegsNeil Chandlersent from my
phoneOn 15 Aug 2011, at 18:13, "MacGregor, Ian A." wrote:> It may be that
Oracle has incorrect statistics concerning your I/O system, or even if those
statistics are good, has still misjudged its capabilities. It may be the OS
statistics were gathered at an inappropriate time. I am of the opinion that
Oracle still overrates full table scans as compared to index lookups. There is
an initialization parameter which addresses this.> > optimizer_index_cost_adj>
> > --//www.freelists.org/webpage/oracle-l
Other related posts:
