Re: SQL Trace on very busy server - experiences, warnings, horror stories ...

"Dusan Bolek" <pagesflames_at_usa.net> wrote in message news:1e8276d6.0311210801.2e5bd33a_at_posting.google.com...
> Greetings,
>
> does anyone here has an experience with using SQL_TRACE = True on
> quite busy business critical system?
> Right now, one guy here wants to use SQL Trace on 24x7 business
> critical server with up to 4000 concurrent users. Database is 8.1.7EE
> 64-bit on Solaris (SF15k). During peaks, CPUs occupation is about 80%,
> with day averages between 50% - 60%.
> My feelings about this are somehow mixed. I fear that we can run into
> big trouble, because performance of system can go down and client's
> voices high.
> The problem with SQL_TRACE is that it is a static parameter, so if we
> will encounter any problem we will be forced to restart our database
> during peak hours. So for me is really important to estimate
> probability that we will need to do this. I can think about switching
> SQL Trace off and restarting server as backup solution with 10%
> probability, but I can't accept this as fifty-fifty scenario.
> I've used SQL Trace in past, but never on server of such importance
> and with load that is quite high. Do you have any experiences with
> this? I would accept even horror stories and suggestions like "never
> do that, you fool!" :-)
>
> P.S. Maybe I'm too cautious, but I really dislike this whole idea.
> However, I can't operate just with my feelings. I need some solid
> ground to make qualified decision.

I dislike the idea as well, for these reasons.

1. Its an overhead.
2. It isn't targeted so it cannot give you useful data
3. what will you do with 4000*500mb trace files?
4. statspack will give you systemwide data and information as well.
5. you should be looking at problem sessions or problem processes, these are exactly amenable to tracing.

What is the business case for making this change and what happened in your test with 4000 simulated users?

--
Niall Litchfield
Oracle DBA
Audit Commission UK
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