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.
-- --Original Message-- --
From: oracle-l-bounce@(protected)
[mailto:oracle-l-bounce@(protected)]On Behalf Of Cary Millsap
Sent: Tuesday, August 03, 2004 12:09 PM
To: oracle-l@(protected)
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 =
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, =
locks,
and everything else that a process competes for. What I see so =
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 =
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 =
each
of the same 100 users). CPU utilization is locked perpetually at 100%, =
and
the system is deadlocked.
In many cases, the original 80-second user can be fixed to run in a =
second
or less by eliminating wasteful work. When this is the case, the end =
result
is that users are ecstatic about response time, and the next server =
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 =
Charlotte
- SQL Optimization 101: 7/26 Washington DC, 8/16 Minneapolis, 9/20 =
Hartford
- Hotsos Symposium 2005: March 6-10 Dallas
- Visit www.hotsos.com for schedule details...
-- --Original Message-- --
From: oracle-l-bounce@(protected) =
[mailto:oracle-l-bounce@(protected)]
On Behalf Of Freeman, Donald
Sent: Tuesday, August 03, 2004 10:20 AM
To: oracle-l@(protected)
Subject: RE: Oracle 9.2.0.5 "10046 " Tracing Causes Server Crash on =
Windows
2000?
We were hoping to improve query performance with parallel although it =
=3D
may not be necessary in all circumstances. Regarding parallel is it =3D
better to pick and choose what activities are performed in parallel? I =
=3D
think we 've basically defaulted it on after our performance improved in =
=3D
the areas we were concerned about. What about V$PARAMETER error? Is =3D
that significant? It keeps showing up in the alert log.=3D20
We had two occassions last week when I had to reboot the server. The =
=3D
first was recorded in the logs I provided. The second was when I =3D
arrived in the morning Friday and couldn 't log in. I couldn 't find any =
=3D
errors recorded anywhere. We installed 9.2.0.5 on Tuesday the 27th.
-- --Original Message-- --
From: oracle-l-bounce@(protected)
[mailto:oracle-l-bounce@(protected)]On Behalf Of Tanel P=3DF5der
Sent: Tuesday, August 03, 2004 10:46 AM
To: oracle-l@(protected)
Subject: Re: Oracle 9.2.0.5 "10046 " Tracing Causes Server Crash on
Windows 2000?
It seems that, you are using parallel query and =3D
cursor_sharing=3D3Dforce|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
my
experience).
Tanel.
-- -- Original Message -- --=3D20
From: "Freeman, Donald " <dofreeman@(protected) >
To: "Oracle-L (E-mail) " <oracle-l@(protected) >
Sent: Tuesday, August 03, 2004 5:26 PM
Subject: Oracle 9.2.0.5 "10046 " Tracing Causes Server Crash on Windows =
=3D
2000?
> I am finally getting to practice some of the tracing functionality =3D
that =3D3D
> is discussed here and ran into something I haven 't seen dicussed here. =
=3D
=3D3D
> We had a complaint about a query that performs inconsistently and I =
=3D
=3D3D
> enabled my session trigger on user logon to capture it. The server =
=3D
=3D3D
> failed at a point shown below. The first entry is the alert log =3D
entry. =3D3D
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