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 <wisernet100_at_yahoo.com> 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" <Waleed.Khedr_at_FMR.COM> 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
> <ORACLE-L_at_fatcity.com>
> > > 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
> <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:
> >
> === message truncated ===
>
>
> __________________________________________________
> 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: Rachel Carmichael
> INET: wisernet100_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
> 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).
Connor McDonald
http://www.oracledba.co.uk (mirrored at
http://www.oradba.freeserve.co.uk)
"Some days you're the pigeon, some days you're the statue"
Do You Yahoo!?
Everything you'll ever need on one web page
from News and Sport to Email and Music Charts
http://uk.my.yahoo.com
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: =?iso-8859-1?q?Connor=20McDonald?=
INET: hamcdc_at_yahoo.co.uk
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).
Received on Wed Apr 24 2002 - 04:33:26 CDT