Re: X$ksmsp (OSEE 10.2.0.2 on Solaris 8)

hi Gogala:

Do you have some meterials or test for this? I mean "selecting from tables like that usually means to acquire a latch for each row. "

Does querying each x$ table need to hold latch?

Thanks

On 6/27/06, Mladen Gogala <gogala_at_sbcglobal.net> wrote:
>
>
> On 06/27/2006 08:12:07 AM, Lawie, Duncan wrote:
> > Charles,
> >
> > I agree that a row in x$ksmsp should equal a single memory chunk - but
> is it possible that there is a chunk with an outrageous value? I don't
> recall that particular case, but I have seen x$ksmsp sum to values
> significantly larger than the size of the SGA.
> >
> > In addition, I have also had significant performance issues on a
> production system when selecting on this table in a very busy system which
> is severely fragmented.
> >
> > Cheers,
> > Duncan.
> >
>
>
> Guys, selecting from tables like that usually means to acquire a latch for
> each row. If the table points to the real chunks of SGA, those chunks must
> be protected from changing during select. Every one of them. That means
> latch.
>
> I don't see any pressing need to use the table, especially not if the
> table
> is undocumented. I must say that Oracle10gR2 is marvelously instrumented
> and
> equipped with the documented performance tables. It misses just one thing:
> "run my stuff faster" parameter, which will probably be available in the
> next
> release as an undocumented parameter, will be tweaked by the bravest among
> us,
> causing, of course, ORA-0600 and ORA-7445 errors. Parameter will
> eventually
> become useful in the Oracle21R3.
>
>
> --
> Mladen Gogala
> http://www.mgogala.com
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

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