Re: Currval and buffer gets

Thank all of you for the replies.
Unfortunately the program is in c++.

Gaja, I will forward your suggestion to the development team.

Yechiel Adar
Mehish

• Original Message ----- To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Sent: Sunday, April 21, 2002 8:28 PM

> Hi Yechiel,
>
> Any full-table-scan in Oracle 8i (or below) consumes 4
> LIOs to the segment header. This number has reduced to
> 2 in 9i. Given that the 1 row that you are going after
> is in 1 data block, there is 1 LIO for the data block
> itself, given you a total of 5 LIOs. You can verify
> this by setting 10046 for the session and looking at
> the trace output.
>
> The workaround is to reference x$dual in your
> application. Alternatively, you can create a view on
> x$dual, create a synonym for it and then go from
> there. You will incur some I/O for the first access of
> the query (with the synonym), but subsequent accesses
> will incur 0 LIOs against x$dual.
>
> Cheers,
>
> Gaja
> --- Yechiel Adar <adaryechiel_at_hotmail.com> wrote:
> > I did two statspack snapshots, one hour and forty
> > minutes apart.
> > Then I generated a report and loaded it into
> > oraperf.com.
> > In the report I saw that the two SQL statements that
> > where executed the most
> > times where:
> >
> > Select xxxx.currval from dual;
> >
> > Select xxxx.nextval from dual;.
> >
> > Each one was executed about 90,000 times with 5
> > buffer gets per execution.
> > The net result was about 950,000 buffer get for
> > nextval and currval.
> >
> > My question is:
> > Why should there be about 5 buffer gets per
> > execution?
> >
> > Yechiel Adar
> > Mehish
> > --
> > Please see the official ORACLE-L FAQ:
> > http://www.orafaq.com
> > --
> > Author: Yechiel Adar
> > INET: adaryechiel_at_hotmail.com
> >
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>
> =====
> Gaja Krishna Vaidyanatha
> Director, Storage Management Products,
> Quest Software, Inc.
> Co-author - Oracle Performance Tuning 101
> http://www.osborne.com/database_erp/0072131454/0072131454.shtml
>
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> Author: Gaja Krishna Vaidyanatha
> INET: oraperfman_at_yahoo.com
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-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Yechiel Adar
  INET: adaryechiel_at_hotmail.com

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
San Diego, California        -- Public Internet access / Mailing Lists
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