Re: Anyone seen weblogic do this?
- From: J.Velikanovs@xxxxxxxx
- To: oracle-l@xxxxxxxxxxxxx
- Date: Mon, 5 Jul 2004 15:16:40 +0300
>> In 8i there is no x$dual, there you could use a single table hash
cluster or IOT with relevant view on it to reduce dual cost (an unique
scan on single block IOT akes only 1 LIO compared to 3 that FTS makes on a
single block table).
You definitely know, but in any case FYI:
=====================================================
SYS:BUKA> select rowid from dual;
ROWID
------------------
AAAADDAABAAAAHSAAA
SYS:BUKA> create view mydual as select * from dual where
rowid='AAAADDAABAAAAHSAAA';
View created.
SYS:BUKA> set autotrace on stat
SYS:BUKA> select sysdate from mydual;
SYSDATE
---------
05-JUL-04
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
1 consistent gets
0 physical reads
0 redo size
195 bytes sent via SQL*Net to client
188 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SYS:BUKA>
=====================================================
Jurijs
9268222
============================================
http://otn.oracle.com/ocm/jvelikanovs.html
Tanel Põder <tanel.poder.003@xxxxxxx>
Sent by: oracle-l-bounce@xxxxxxxxxxxxx
02.07.2004 16:31
Please respond to oracle-l
To: <oracle-l@xxxxxxxxxxxxx>
cc:
Subject: Re: Anyone seen weblogic do this?
If you cannot eliminate these excessive queries by any means, then you
could
relieve the performance hit by having a local dual synonym pointing to a
view uner sys schema whish queries x$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@xxxxxxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
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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