Concurrency test from 1 => 10 on Solaris 8.1.7.3
revealed no crashes - using
#!/bin/ksh
for i in 1 2 3 4 ...
do
sqlplus u/p @the_test.sql &
done
hth
connor
--- Rachel Carmichael <[EMAIL PROTECTED]> wrote:
> as simultaneously as I could make it on W2K, 9.0.1.2
> (which means the
> first one was running as I started the second one)
>
> no problems. Now I ran as sys and changed it to
> x$dual because I got
> errors (table or view not found) when I ran as
> system and used x_$dual
> so I don't know if that changed the test
>
>
> --- "Khedr, Waleed" <[EMAIL PROTECTED]> wrote:
> > Never mess up with Oracle's memory:
> >
> > It seems that x$dual is not designed for
> concurrent access. When I
> > try to
> > run the code below in two simultaneous windows the
> first one comes
> > back and
> > the second crash (8173):
> >
> > declare
> > nn number;
> > ss1 date;
> > ss2 date;
> > begin
> > ---
> > ss1 := sysdate;
> > for i in 1..100000 loop
> > select 2 into nn from sys.x_$dual;
> > end loop;
> > ss2 := sysdate;
> > dbms_output.put_line('run time using table dual in
> > centiseconds='||(ss2 -
> > ss1 ) * 24 * 60 * 60 * 100);
> > end;
> >
> >
> > If the x$dual gets replaced by dual it works fine.
> >
> > Can any one duplicate this?
> >
> >
> > Thanks
> >
> >
> > Waleed
> >
> >
> >
> > -----Original Message-----
> > Sent: Tuesday, April 23, 2002 6:49 PM
> > To: Multiple recipients of list ORACLE-L
> >
> >
> > I am writing a paper on application efficiency and
> I have a number of
> > simple
> > tests in that paper that illustrates that in a
> very efficient
> > application
> > the
> > switch to x$dual can make around a 70-80 percent
> improvent. But
> > beaware: the
> > test suite only accesses x$dual and not other
> tables so the impact is
> > large
> > and the application is written in the most
> efficient way. Running
> > the same
> > test but in a worse efficiency case. shows only a
> 2-3 percent gain
> > ......
> >
> > Anjo.
> >
> >
> > "Khedr, Waleed" wrote:
> >
> > > Can you guys tell me about all the overhead to
> resolve the view
> > definition
> > > to reach the magical X$dual table?
> > >
> > > Waleed
> > >
> > > -----Original Message-----
> > > Sent: Tuesday, April 23, 2002 12:58 PM
> > > To: Multiple recipients of list ORACLE-L
> > >
> > > Redefine the view to work on dual and pay the
> price !!!
> > > Checked it on oracle 8.1.6 and 9.0.1.
> > > I will take the risk that maybe in some future
> date this will not
> > work
> > > if it can save a lot of resources now.
> > >
> > > Yechiel Adar
> > > Mehish
> > >
> > > ----- Original Message -----
> > > To: Multiple recipients of list ORACLE-L
> <[EMAIL PROTECTED]>
> > > Sent: Tuesday, April 23, 2002 3:13 PM
> > >
> > > > what would you do if Oracle removed this
> x$dual or made it
> > multiple row
> > > > table in future upgrades?
> > > >
> > > > -----Original Message-----
> > > > To: Multiple recipients of list ORACLE-L
> > > > Sent: 4/23/02 4:08 AM
> > > >
> > > > Hello Gaja
> > > >
> > > > Thanks for the detailed info.
> > > > I created a view and did grant to public.
> > > > I did 10 selects and they did only 2 buffers
> get.
> > > > BTW - describe on x$dual does not work but
> select * works.
> > > >
> > > > Yechiel Adar
> > > > Mehish
> > > >
> > > > ----- Original Message -----
> > > > To: Multiple recipients of list ORACLE-L
> <[EMAIL PROTECTED]>
> > > > Sent: Monday, April 22, 2002 8:15 PM
> > > >
> > > >
> > > > > Hello Yechiel,
> > > > >
> > > > > X$DUAL is an Oracle-internal table "in the
> SGA" and
> > > > > will not be shown in an ALL_OBJECTS listing.
> > > > > Obviously, you need to be SYS to see this.
> You can do
> > > > > a describe as SYS and you will see it. Which
> is the
> > > > > reason why I recommended creating a view and
> a public
> > > > > synonym on the view, so that the application
> may
> > > > > reference it without any issues.
> > > > >
> > > > > Cheers,
> > > > >
> > > > > Gaja
> > > > >
> > > > > --- Yechiel Adar <[EMAIL PROTECTED]>
> wrote:
> > > > > > Hello Gaja
> > > > > >
> > > > > > I could not find x$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
> > > > > > <[EMAIL PROTECTED]>
> > > > > > 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
> <[EMAIL PROTECTED]> 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: [EMAIL PROTECTED]
> > > > > > > >
> > > > > > > > Fat City Network Services -- (858)
> 538-5051
> > > > > > FAX:
> >
> === message truncated ===
>
>
> __________________________________________________
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> Please see the official ORACLE-L FAQ:
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> Author: Rachel Carmichael
> INET: [EMAIL PROTECTED]
>
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=====
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http://www.oracledba.co.uk (mirrored at
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"Some days you're the pigeon, some days you're the statue"
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