Re: optimizer parameters

From: Tim Gorman <>
Date: Sun, 24 Apr 2011 12:10:03 -0600
Message-ID: <>


I've similar success stories and considered responding in kind, but my mood this weekend yielded the more resigned, apathetic, fatalistic response -- much to my own very public chagrin.  Thanks for the correction and for filling the breach!

Best wishes,


On 4/24/2011 11:49 AM, Stephane Faroult wrote:

On the other hand, we've all been here.  The vendor is likely to dig in their heels, demand that the parameters be changed, ignore your well-reasoned advice, and your management will override you because legal advised them to, and that's that.  Just the way it is... ...can you see that this weekend hasn't been nearly long enough?  :-)

I beg to disagree. I once had a problem with a query that was taking a very long time on a development database with relatively low volumes compared to the 4 minutes it was taking on the production database (three times bigger). The DBAs were instructed to do what they could to have identical plans in both cases. I rewrote the query, and demonstrated that it could get the result in 2 or 3 seconds in dev - and that by the way it was taking now 30s in prod. Sent the test-case back, never heard of them after that.


On 4/24/2011 6:22 AM, ed lewis wrote:
   I'm curious what other peoples's experience, suggestions
are in regard to the use of the  "optimizer_index_caching", and
"optimizer_index_cost_adj" parameters.
    As a general practice, I leave them at their defaults, unIess
the vendor specifically requires that they be modifed. I  use
system statistics instead. I haven't find the need to do otherwise.
I've tested these parameters on queries, and have received various results.
In some cases, it made use of an index, and in other cases,
it had no impact.
    I'm not a fan of changing this in midstream for an app
that has been running for almost 2 years. This particular vendor
is asking to modify this, as a possible solution to a slow-running
query. I'm pushing back, and would rather address this in other
ways, such as tracing the query, and go from there.
    Your input is appreciated.
solaris 10
rac, asm
-- Received on Sun Apr 24 2011 - 13:10:03 CDT

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