Re: Using PQ in FTS

If mixed access (meaning both buffered and direct access) is done on objects where DML is happening, it can result in buffer busy waits because extents needs to be checkpointed before direct access can occure.

Seen a great deal of buffer busy waits in 9.2.0.6/linux where concurrent DML queries got downgraded to serial due to the parallel automatic tuning.

This is probably true for higher versions (because of how PX is implemented) of the database, but haven't tested it.

frits

On 3/27/07, John Kanagaraj <john.kanagaraj_at_gmail.com> wrote:
>
> Amir,
>
> Have a look at http://oracledoug.com/px.html - Be aware that you set
> PQ's init.ora parameters properly, specially to limit the number of PQ
> servers: Otherwise, you might end up choking on CPU on unbound
> usage...
>
> John
>
> On 3/26/07, Hameed, Amir <Amir.Hameed_at_xerox.com> wrote:
> >
> >
> > No, PQ used by batch jobs.
> >
> >
> > ________________________________
> > From: Arul Ramachandran [mailto:contactarul_at_gmail.com]
> > Sent: Monday, March 26, 2007 1:08 PM
> > To: Hameed, Amir
> > Cc: oracle-l_at_freelists.org
> > Subject: Re: Using PQ in FTS
> >
> >
> > I was going to say unintended block cleanouts.. but then glanced
> Jonathan
> > Lewis' book page 30 where it mentions 'segment checkpoint', that sounds
> > almost like block cleanouts....
> >
> > I suppose you did not mean PQ will be used by OLTP queries...
> >
> >
> > Arul
> >
> >
> >
> > On 3/23/07, Hameed, Amir <Amir.Hameed_at_xerox.com> wrote:
> > > Folks,
> > > If there are statements where FTS on large tables is unavoidable due
> to
> > > the logic in the statements, is there a downside of using PQ to scan
> > > those tables? Jonathan has mentioned one caution on page 30 of his
> book
> > > but are there any other issues that one must be aware of ? The RDBMS
> > > version are 9.2.0.6 and 10.2.0.2.
> > >
> > > Thanks
> > > Amir
> > >
> > > --
> > > http://www.freelists.org/webpage/oracle-l
> > >
> > >
> > >
> >
> >
> >
> > --
> > Arul
>
>
> --
> John Kanagaraj <><
> DB Soft Inc
> Phone: 408-970-7002 (W)
>
> ** The opinions and facts contained in this message are entirely mine
> and do not reflect those of my employer or customers **
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

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