Re: OPTIMIZER MODE
- From: Ron Chennells <ron.chennells@xxxxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Tue, 06 Jul 2010 13:05:27 +0100
Ram
I worked on a SIEBEL CRM system a while ago.
SIEBEL sets first_rows_10 at the session level for it's connections (mostly),
May be worth seeing if you could set session level parameters in your case.
Quoting Frits Hoogland <frits.hoogland@xxxxxxxxx>:
Ram,
Jonathan Lewis has a good blogpost about this:
http://jonathanlewis.wordpress.com/2008/11/11/first_rows_n/. Randolf
Geist has also done a presentation on FIRST_ROWS (actually
FIRST_ROWS_n to be precise) on last year's UKOUG.
In essence:
a) general advise is to use ALL_ROWS, unless your system generally
only uses the first rows the query returns. Most systems use the
entire query resultset.
b) if you already have your system running on FIRST_ROWS, a change
of optimizer mode will impact your entire system, so not just change
it.
frits
On Jul 6, 2010, at 1:17 PM, Ram K wrote:
Listers,
We have a new 11g based hybrid application that a third party
vendor is configuring. We observe some slowness in the response
times. I do not see any slow sql in v$sql. The vendor is
recommending that we set the OPTIMIZER_MODE to FIRST_ROWS to get
better response times, among other parameter changes. I have read
in few sources that FIRST_ROWS is not generally used, with oracle
itself using ALL_ROWS. Can anyone advise?
--
Thanks,
Ram.
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