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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Oracle 9.2.0.5 "10046" Tracing Causes Server Crash on Windows 2000?
We haven't seen any negative results from using parallel. The db is a =
datawarehouse with no more than 4 concurrent users connecting through =
Cognos during the day and no activity at night outside the Informatica =
ETL process.=20
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Cary Millsap
Sent: Tuesday, August 03, 2004 12:09 PM
To: oracle-l_at_freelists.org
Subject: RE: Oracle 9.2.0.5 "10046" Tracing Causes Server Crash on
Windows 2000?
Bugs and other undocumented behaviors notwithstanding, using parallel features produces one specific and very important risk that you should understand.
When you N-way parallelize a process, you convert a single process into =
=3D
N
distinct processes (at least N--in Oracle, it's actually 2N+1). Each of
these processes now competes for CPU time, memory busses, latches, =3D
locks,
and everything else that a process competes for. What I see so =3D
frequently is
the following...
What the user wants: My user action runs in 80 seconds, so I'll 4-way parallelize it in attempt to make it run in 20 seconds.
What really happens: Yesterday 100 users made 100 database connections =
=3D
at a
time, which used 80% of the CPU capacity on the server. Today, the same
users are making 900 database connections at a time (2*4+1 sessions for =
=3D
each
of the same 100 users). CPU utilization is locked perpetually at 100%, =
=3D
and
the system is deadlocked.
In many cases, the original 80-second user can be fixed to run in a =3D
second
or less by eliminating wasteful work. When this is the case, the end =3D
result
is that users are ecstatic about response time, and the next server =3D
upgrade
can be deferred by several months because the system is running at
significantly reduced CPU utilization.
So, what's the best way to tune a parallel operation? Deactivate the parallelization, and optimize the remaining serial operation. :)
Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com
* Nullius in verba *
Upcoming events:
- Performance Diagnosis 101: 8/10 Boston, 9/14 San Francisco, 10/5 =3D
Charlotte
- SQL Optimization 101: 7/26 Washington DC, 8/16 Minneapolis, 9/20 =3D
Hartford
- Hotsos Symposium 2005: March 6-10 Dallas
- Visit www.hotsos.com for schedule details...
-----Original Message-----
From: oracle-l-bounce_at_freelists.org =3D
[mailto:oracle-l-bounce_at_freelists.org]
On Behalf Of Freeman, Donald
Sent: Tuesday, August 03, 2004 10:20 AM
To: oracle-l_at_freelists.org
Subject: RE: Oracle 9.2.0.5 "10046" Tracing Causes Server Crash on =3D
Windows
2000?
We were hoping to improve query performance with parallel although it =
=3D
=3D3D
may not be necessary in all circumstances. Regarding parallel is it =
=3D3D
better to pick and choose what activities are performed in parallel? I =
=3D
=3D3D
think we've basically defaulted it on after our performance improved in =
=3D
=3D3D
the areas we were concerned about. What about V$PARAMETER error? Is =
=3D3D
that significant? It keeps showing up in the alert log.=3D3D20
We had two occassions last week when I had to reboot the server. The =
=3D
=3D3D
first was recorded in the logs I provided. The second was when I =3D3D
arrived in the morning Friday and couldn't log in. I couldn't find any =
=3D
=3D3D
errors recorded anywhere. We installed 9.2.0.5 on Tuesday the 27th.
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Tanel P=3D3DF5der
Sent: Tuesday, August 03, 2004 10:46 AM
To: oracle-l_at_freelists.org
Subject: Re: Oracle 9.2.0.5 "10046" Tracing Causes Server Crash on
Windows 2000?
It seems that, you are using parallel query and =3D3D
cursor_sharing=3D3D3Dforce|similar
here, it might be that the problem occurs when all of these features
"collide". Do you need your query to run in parallel? (parallel option
triggers lots of bugs, including data/query result corruption ones, in =
=3D
=3D3D
my
experience).
Tanel.
> I am finally getting to practice some of the tracing functionality =
=3D3D
that =3D3D3D
> is discussed here and ran into something I haven't seen dicussed here. =
=3D
=3D3D
=3D3D3D
> We had a complaint about a query that performs inconsistently and I =
=3D
=3D3D
=3D3D3D
> enabled my session trigger on user logon to capture it. The server =
=3D
=3D3D
=3D3D3D
> failed at a point shown below. The first entry is the alert log =3D3D
entry. =3D3D3D
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