Re: Init.ora .. OPTIMIZER parm: optimizer_index_cost_adj

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 Have you tried increasing the hash_area_size, or db_file_multiblock_read_count? I've found altering these at the session level sometimes makes the optimizer prefer a hash_join, though not always. Sometimes I wonder where it's brain is.

  jkstill_at_cybcon.com wrote:

I've used this in an attempt to make the optimizer prefer a hash join over a nested loops join.

The desired results were not achieved.

Jared

On Tue, 30 Jan 2001 bruce.taneja_at_mcd.com wrote:

>
>
> Has any one messed with
> optimizer_index_cost_adj
> on 8.1.7 ??
>
> The default is 100, but my boss thinks 10 is a better value for Cost based Opmtzr..
> doesn't make any sense to me.. why would reducing the cost of using an
> optimizer make it more CBO or go faster.. what if its a large table?
>
> Is it a good strategy to reduce this value to 10 or so ..
>
> any one played with this on a 30GB database ? or any other size db?
>
> thanks, Bruce
>
>
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> Author:
> INET: bruce.taneja_at_mcd.com
>
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<P> Have you tried increasing the hash_area_size, or db_file_multiblock_read_count? I've found altering these at the session level sometimes makes the optimizer prefer a hash_join, though not always. Sometimes I wonder where it's brain is.<BR>
<P>&nbsp; <B><I>jkstill_at_cybcon.com</I></B> wrote: <BR>
<BLOCKQUOTE style="BORDER-LEFT: #1010ff 2px solid; MARGIN-LEFT: 5px; PADDING-LEFT: 5px"><BR>I've used this in an attempt to make the optimizer prefer a hash join<BR>over a nested loops join.<BR><BR>The desired results were not achieved.<BR><BR>Jared<BR><BR>On Tue, 30 Jan 2001 bruce.taneja@mcd.com wrote:<BR><BR>&gt;<BR>&gt;<BR>&gt; Has any one messed with<BR>&gt; optimizer_index_cost_adj<BR>&gt; on 8.1.7 ??<BR>&gt;<BR>&gt; The default is 100, but my boss thinks 10 is a better value for Cost based Opmtzr..<BR>&gt; doesn't make any sense to me.. why would reducing the cost of using an<BR>&gt; optimizer make it more CBO or go faster.. what if its a large table?<BR>&gt;<BR>&gt; Is it a good strategy to reduce this value to 10 or so ..<BR>&gt;<BR>&gt; any one played with this on a 30GB database ? or any other size db?<BR>&gt;<BR>&gt; thanks, Bruce<BR>&gt;<BR>&gt;<BR>&gt; --<BR>&gt; Please see the official ORACLE-L FAQ: http://www.orafaq.com<BR>&gt; --<BR>&gt; Author:<BR>&gt; INET: b!
ruce.taneja@mcd.com<BR>&gt;<BR>&gt; Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051<BR>&gt; San Diego, California -- Public Internet access / Mailing Lists<BR>&gt; --------------------------------------------------------------------<BR>&gt; To REMOVE yourself from this mailing list, send an E-Mail message<BR>&gt; to: ListGuru@fatcity.com (note EXACT spelling of 'ListGuru') and in<BR>&gt; the message BODY, include a line containing: UNSUB ORACLE-L<BR>&gt; (or the name of mailing list you want to be removed from). You may<BR>&gt; also send the HELP command for other information (like subscribing).<BR>&gt;<BR><BR>-- <BR>Please see the official ORACLE-L FAQ: http://www.orafaq.com<BR>-- <BR>Author: <BR>INET: jkstill@cybcon.com<BR><BR>Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051<BR>San Diego, California -- Public Internet access / Mailing Lists<BR>--------------------------------------------------------------------<BR>To REMOVE yourself from this m!
ailing list, send an E-Mail message<BR>to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in<BR>the message BODY, include a line containing: UNSUB ORACLE-L<BR>(or the name of mailing list you want to be removed from). You may<BR>also send the HELP command for other information (like subscribing).</BLOCKQUOTE><p><br><hr size=1><b>Do You Yahoo!?</b><br>
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