Hi Yechiel,
Below is a spool file from my 8.1.7 database. I am
logged in as SYS and I am able to do a "DESC" on
X$DUAL. Wonder why it did not work on yours.
SQL> desc x$dual
Name Null?
Type
- --------
ADDR
RAW(4)
INDX
NUMBER
INST_ID
NUMBER
DUMMY
VARCHAR2(1)
SQL> spool off
Cheers,
Gaja
- Yechiel Adar <adaryechiel_at_hotmail.com> wrote:
> Hello Gaja
>
> Thanks for the detailed info.
> I created a view and did grant to public.
> I did 10 selects and they did only 2 buffers get.
> BTW - describe on x$dual does not work but select *
> works.
>
> Yechiel Adar
> Mehish
>
> ----- Original Message -----
> To: Multiple recipients of list ORACLE-L
> <ORACLE-L_at_fatcity.com>
> Sent: Monday, April 22, 2002 8:15 PM
>
>
> > Hello Yechiel,
> >
> > X$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
> > > > > 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
> > > > > 'ListGuru') and in
> > > > > the message BODY, include a line containing:
> > > UNSUB
> > > > > 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
> > > >
> > >
> >
>
> > > > To REMOVE yourself from this mailing list,
> send an
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> of
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> > > >
>
=== message truncated ===
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 Tue Apr 23 2002 - 13:23:29 CDT
