Hello Yechiel,
X$DUAL is an Oracle-internal table "in the SGA" and
will not be shown in an ALL_OBJECTS listing.
Obviously, you need to be SYS to see this. You can do
a describe as SYS and you will see it. Which is the
reason why I recommended creating a view and a public
synonym on the view, so that the application may
reference it without any issues.
Cheers,
Gaja
- Yechiel Adar <adaryechiel_at_hotmail.com> wrote:
> Hello Gaja
>
> I could not find x$dual. Did select on all_objects
> got zip.
> Oracle 8.1.6.3.4 on NT.
>
> 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
> > >
> > > Fat City Network Services -- (858) 538-5051
> FAX:
> > > (858) 538-5051
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> > >
> >
>
> > > To REMOVE yourself from this mailing list, send
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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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> > --
> > Please see the official ORACLE-L FAQ:
> http://www.orafaq.com
> > --
> > Author: Gaja Krishna Vaidyanatha
> > INET: oraperfman_at_yahoo.com
> >
> > Fat City Network Services -- (858) 538-5051
> FAX: (858) 538-5051
> > San Diego, California -- Public Internet
> access / Mailing Lists
> >
>
> > To REMOVE yourself from this mailing list, send an
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> > to: ListGuru_at_fatcity.com (note EXACT spelling of
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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
>
> To REMOVE yourself from this mailing list, send an
> E-Mail message
> to: ListGuru_at_fatcity.com (note EXACT spelling of
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> 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).
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
Do You Yahoo!?
Yahoo! Games - play chess, backgammon, pool and more
http://games.yahoo.com/
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Gaja Krishna Vaidyanatha
INET: oraperfman_at_yahoo.com
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
San Diego, California -- Public Internet access / Mailing Lists
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Received on Mon Apr 22 2002 - 13:15:07 CDT
