Hi Dan and list,
Here is the output from a test after setting 10046 at
level 12. Please tell me whether this is really 0 or
not accounted for. If it is not accounted for, then I
stand corrected.
Thanks,
Gaja
----Trace file output starts here----
*** 2002-04-22 16:04:14.090
*** SESSION ID:(11.752) 2002-04-22 16:04:14.060
PARSING IN CURSOR #1 len=70 dep=0 uid=0 oct=42 lid=0
tim=5655178 hv=347037164 ad='51d70a0'
alter session set events '10046 trace name context
forever, level 12'
END OF STMT
EXEC
#1:c=2,e=4,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=4,tim=5655179
WAIT #1: nam='SQL*Net message to client' ela= 0
p1=1111838976 p2=1 p3=0
*** 2002-04-22 16:04:25.617
WAIT #1: nam='SQL*Net message from client' ela= 1152
p1=1111838976 p2=1 p3=0
PARSING IN CURSOR #1 len=21 dep=0 uid=0 oct=3 lid=0
tim=5656331 hv=2119980703 ad='51d5564'
select * from x$dual
END OF STMT
PARSE
#1:c=0,e=0,p=0,cr=0,cu=0,mis=1,r=0,dep=0,og=4,tim=5656331
BINDS #1:
EXEC
#1:c=0,e=0,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=4,tim=5656332
WAIT #1: nam='SQL*Net message to client' ela= 0
p1=1111838976 p2=1 p3=0
FETCH
#1:c=0,e=0,p=0,cr=0,cu=0,mis=0,r=1,dep=0,og=4,tim=5656332
WAIT #1: nam='SQL*Net message from client' ela= 2
p1=1111838976 p2=1 p3=0
FETCH
#1:c=0,e=0,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=4,tim=5656334
WAIT #1: nam='SQL*Net message to client' ela= 0
p1=1111838976 p2=1 p3=0
WAIT #1: nam='SQL*Net message from client' ela= 815
p1=1111838976 p2=1 p3=0
STAT #1 id=1 cnt=1 pid=0 pos=0 obj=0 op='FIXED TABLE
FULL X$DUAL '
----Trace file output ends here----
- Danisment Gazi Unal <dunal_at_ubTools.com> wrote:
> Hello Gaja,
>
> am I missing something ?
>
> is it 0 logical IO indeed ? or it's not accounted
> for X$ tables ?
>
> regards...
>
>
>
> Gaja Krishna Vaidyanatha wrote:
>
> > 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
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> > > 'ListGuru') and in
> > > the message BODY, include a line containing:
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> > > (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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> > to: ListGuru_at_fatcity.com (note EXACT spelling of
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> > the message BODY, include a line containing: UNSUB
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> > (or the name of mailing list you want to be
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> > also send the HELP command for other information
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>
> --
> Danisment Gazi Unal
> http://www.ubTools.com
>
>
> --
> Please see the official ORACLE-L FAQ:
> http://www.orafaq.com
> --
> Author: Danisment Gazi Unal
> INET: dunal_at_ubTools.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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> (or the name of mailing list you want to be removed
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> 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 - 19:30:01 CDT
