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
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