| Oracle FAQ | Your Portal to the Oracle Knowledge Grid | |
 |
 | |||
| Oracle FAQ | Your Portal to the Oracle Knowledge Grid | |
|
| |||
Home -> Community -> Mailing Lists -> Oracle-L -> Re: Re: max parallel query
hmmm... when i run statspack during a big load. most of my waits are from
redo log waits and read from a staging datafile. we have all of our
datafiles on the same I/O mount. We are using a Network Appliance back end
with asynch I/O.
are you telling me that putting these files on seperate mount points will have no effect? I dont quite follow asynch I/O. I dont have much of a hard ware OS background.
I cant find any docs or articles on how to tune Parallel Operations. All I
see are basic syntax. Do you know of any?
----- Original Message -----
To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
Sent: Thursday, September 18, 2003 5:24 PM
> If you want rules of thumb, then take CPU_COUNT+1 up to CPU_COUNT *2.
>
> I think LIO & PIO ratio is irrelevant, the most important is whether you
are
> able to construct optimal parallel execution plan, e.g. avoid excessive
> parallel slave messaging & waiting. This is mostly design and SQL issue.
>
> The number mount points is irrelevant novadays as well IMHO, especially
when
> you're using async IO, SANs & SAME like architecture. The only thing what
> comes into my mind where splitting into mount points (thus different file
> systems) helps performance wise, is that with more file systems you got
more
> file system locks and you can spread contention for these locks that way.
>
> Tanel.
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> Sent: Thursday, September 18, 2003 9:34 PM
>
>
> > i know there are no magic formulas, but im hoping for something better
> than trial and error. i would assume that parallel query helps most when:
> >
> > 1. are doing work off of multiple mount points.
> > 2. Have alot more LIOs to perform than PIOs(such as sorts).
> >
> > am i close on this?
> > >
> > > From: "M Rafiq" <rafiq9857_at_hotmail.com>
> > > Date: 2003/09/18 Thu PM 01:34:44 EDT
> > > To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> > > Subject: Re: max parallel query
> > >
> > > Tanel,
> > > You are right. There is a param parallel_automatic(I don't remember
> exact
> > > name as I don't have access to database) which should be set to true
and
> let
> > > system decide how many pq slave to be used. For max_parallel_server
> default
> > > is 5 and can be set to higher number which memory and cpu can
handle.
> It
> > > is faster because it uses all system resources at a given time.
> > >
> > > Rarallel process can be used for large batch jobs during off-peak
time.
> > >
> > > Regards
> > > Rafiq
> > >
> > >
> > > Reply-To: ORACLE-L_at_fatcity.com
> > > To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
> > > Date: Thu, 18 Sep 2003 08:39:44 -0800
> > >
> > > There is no simple magic formula how many parallel slaves you should
> have.
> > > It all depends on your CPU and IO utilization. Yes, utilization,
because
> if
> > > your CPUs or IO are running at their limits already, you won't benefit
> from
> > > parallel execution at all. In fact PX may make the situation even
worse,
> > > because it's designed to give you the results the fastest way, not the
> most
> > > efficient way.
> > >
> > > Tanel.
> > >
> > > ----- Original Message -----
> > > To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com>
> > > Sent: Thursday, September 18, 2003 6:15 PM
> > >
> > >
> > > > We run multiple instances on the same server. My understanding is
> > > max_parallel_servers should be set to 4 x CPU. We have 4 CPUs which
> means
> > > 16.
> > > >
> > > > however, does this take into account multiple instances on the same
> > > server?
> > > >
> > > >
> > > > --
> > > > Please see the official ORACLE-L FAQ: http://www.orafaq.net
> > > > --
> > > > Author: <rgaffuri_at_cox.net
> > > > INET: rgaffuri_at_cox.net
> > > >
> > > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com
> > > > San Diego, California -- Mailing list and web hosting
services
> > >
> ---------------------------------------------------------------------> > > > (or the name of mailing list you want to be removed from). You may
> > > > To REMOVE yourself from this mailing list, send an E-Mail message
> > > > to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> > > > the message BODY, include a line containing: UNSUB ORACLE-L
-- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Ryan INET: rgaffuri_at_cox.net Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Thu Sep 18 2003 - 16:44:43 CDT
 |
 |