Re: Anyone seen weblogic do this?

From: <J.Velikanovs_at_alise.lv>
Date: Mon, 5 Jul 2004 15:16:40 +0300
Message-ID: <OF5C89F0F3.8DC704CD-ONC2256EC8.0043CCE2-C2256EC8.0044219A@alise.lv>

>> In 8i there is no x$dual, there you could use a single table hash cluster or IOT with relevant view on it to reduce dual cost (an unique scan on single block IOT akes only 1 LIO compared to 3 that FTS makes on a single block table).
You definitely know, but in any case FYI:

SYS:BUKA> select rowid from dual;

ROWID

AAAADDAABAAAAHSAAA SYS:BUKA> create view mydual as select * from dual where rowid='AAAADDAABAAAAHSAAA';

View created.

SYS:BUKA> set autotrace on stat
SYS:BUKA> select sysdate from mydual;

SYSDATE

05-JUL-04 Statistics

          0  recursive calls
          0  db block gets
          1  consistent gets
          0  physical reads
          0  redo size
        195  bytes sent via SQL*Net to client
        188  bytes received via SQL*Net from client
          3  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed

SYS:BUKA>

Jurijs
9268222

http://otn.oracle.com/ocm/jvelikanovs.html

Tanel Põder <tanel.poder.003_at_mail.ee>
Sent by: oracle-l-bounce_at_freelists.org
02.07.2004 16:31
Please respond to oracle-l

        To:     <oracle-l_at_freelists.org>
        cc: 
        Subject:        Re: Anyone seen weblogic do this?

If you cannot eliminate these excessive queries by any means, then you could
relieve the performance hit by having a local dual synonym pointing to a view uner sys schema whish queries x$dual instead. That way you'd eliminate
3 LIOs per query in 9i (in RAC environment you have to do a little extra trick to query only your instance's row from x$dual).

In 8i there is no x$dual, there you could use a single table hash cluster or
IOT with relevant view on it to reduce dual cost (an unique scan on single block IOT takes only 1 LIO compared to 3 that FTS makes on a single block table).

Tanel.

Original Message ----- From: " L. Trindle Gennari" <initltg_at_earthlink.net> To: <oracle-l_at_freelists.org> Sent: Friday, July 02, 2004 4:08 AM Subject: RE: Anyone seen weblogic do this?

> We ran into that too. Did a sql trace on the whole instance and
discovered
that it was spending 80% of its time doing select 1 from dual.

> ltg
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Received on Mon Jul 05 2004 - 12:49:20 CDT