Re: Deadly OPTIMIZER_SECURE_VIEW_MERGING=TRUE

Hello Robert

I spent two weeks (!) investigating the question. I required support from the vendor, sent them detailed informations. I let users do different tests.
I collected and printed performance numbers, execution plans, looked into waits, used AWR, ADDM, SQL Tuning Advisors, statistics with/without histograms. I was playing with different init parameters (mostly making things even worse). I set up a clone database, did more tests... hey! Let's stop.

As you can see from other replies, you are guessing wrong. (Typical case when people try to complicate obvious things).

If the software is just misbehaving, all this knowledge is for nothing. Almost every query was doing FTS of huge tables, main activity was direct path read. Same application was still installed in the old server running 9i: Execution plans were completely different. So what? It could have been something different than direct path reads, it does not bear any direct logical relationship to the solution. Based on this "knowledge", you would probably... buy more disks?? Wrong!

Thanks anyway.

Rick Denoire

Robert Klemme <shortcutter_at_googlemail.com> wrote:

>On 02.12.2007 02:30, Rick Denoire wrote:
>> Hello
>>
>> After Upgrading a commercial application from 9.2.0.5 to 10.2.0.3 we
>> got a disastrous performance, even though the new server was at least
>> 10 times faster (in terms of CPU). The application manager did not
>> follow test procedures prior to the upgrade, which lead us to a
>> crisis.
>>
>> After some investigation I found that just setting the following
>> parameter resulted in a huge (about 100-fold) performance increase:
>> OPTIMIZER_SECURE_VIEW_MERGING=FALSE
>>
>> See for example:
>> http://www.freelists.org/archives/oracle-l/07-2006/msg00260.html
>>
>> I did not dare to set any hidden parameters yet; perhaps those would
>> have boosted performance even more.
>>
>> Can you confirm that reverting mentioned parameter to the non-default
>> value (FALSE) improves performance so dramatically?
>>
>> What is the rationale of such detrimental default value of the
>> initalization parameter that effectively renders the database
>> "misconfigured"?
>>
>> Are there any other deadly preset parameters I should be aware of
>> after Upgrade to Oracle 10g, according to your experience?
>>
>> Do you really recommend to let Oracle do things automatically? (SGA,
>> PGA, db_file_multibloc_read_count, etc.)
>
>I guess with this information given you cannot expect profound help.
>What did you do to pinpoint the source of the slowness? I mean, do you
>*know* where time is spent? If not, I'd investigate this first before
>doing any changes to the system.
>
>Kind regards
>
> robert
Received on Sun Dec 02 2007 - 13:24:45 CST