RE: Multiple schema and Query performance issue

We are using the Oracle driver and I found the following article that mentioned that oracle already considered this as bug and issued a patch.  

http://blog.nominet.org.uk/tech/Database/2006/06/19/Oracle-ODBC-Performa nce-Problems-in-Oracle-10-2.html?page=comments    

From: Niall Litchfield [mailto:niall.litchfield_at_gmail.com] Sent: Monday, October 16, 2006 1:26 AM
To: Harvinder Singh
Cc: Bobak, Mark; oracle-l
Subject: Re: Multiple schema and Query performance issue  

That sounds a little bit like the way the Microsoft ODBC driver used to behave. If I'm right you might well gain benefits from trying a current Oracle driver (9.2 or 10.2 depending) - you might however also run into support issues with the vendor if this is thrid party (and of course deploying a new Oracle client/odbc driver isn't a simple matter for desktop support people).

On 10/13/06, oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org > wrote:

Mark,

You might be correct, these statement may be generated by odbc and they are taking bulk of the time. Is there any option in odbc that we can disable running this kind of queries or this is normal possible behavior of odbc?

Thanks
--Harvinder

-----Original Message-----

From: Bobak, Mark [mailto:Mark.Bobak_at_il.proquest.com] Sent: Thursday, October 12, 2006 6:35 PM To: Harvinder Singh; oracle-l
Subject: RE: Multiple schema and Query performance issue

You see this recursive SQL on every parse of the SQL, not just the initial (hard) parse?

What language is the application implemented in? Perl/DBI? Java? Pro*C? Something else? Sometimes, client layers can turn on extra levels of checks that cause (sometimes excessive) recursive SQL to occur.

-Mark

--

Mark J. Bobak
Senior Oracle Architect
ProQuest Information & Learning

There is nothing so useless as doing efficiently that which shouldn't be

done at all. -Peter F. Drucker, 1909-2005

-----Original Message-----

From: oracle-l-bounce_at_freelists.org
[mailto: oracle-l-bounce_at_freelists.org
<mailto:oracle-l-bounce_at_freelists.org> ] On Behalf Of Harvinder Singh Sent: Thursday, October 12, 2006 6:30 PM To: Harvinder Singh; oracle-l
Subject: RE: Multiple schema and Query performance issue

Update to the original post

I can also see the same behavior in tkprof output even running the query using table of same schema but using schema name with object name. For example:
Select col1 from schema1.tab1

But I am not able to reproduce the issue when run the same query from sqlplus and this only happens when running the query from application.

-----Original Message-----

From: Harvinder Singh
Sent: Thursday, October 12, 2006 6:14 PM To: oracle-l
Subject: Multiple schema and Query performance issue

Hi,

In our application we have 1 main schema (schema1) and 3 other schema(schema2,schema3,schema4) in nologging mode for performance reasons. Now when I try to run the following query connected as schema1 that should take less than few ms:
SELECT col1,col2
FROM
Schema2.tmp_tab1

Optimizer run the following recursive query and that takes 3-4 sec: SELECT /*+ RULE */ COUNT(*)
FROM
ALL_SYNONYMS WHERE DB_LINK IS NOT NULL AND SYNONYM_NAME=   'TMP_tab1' AND OWNER='SCHEMA2'

Is this a normal behavior when running the query that uses table of another schema as 3-4 sec looks very high time and explain plan showing lot of access to internal tables.
What are the possible solutions to make sure that optimizer don't need to run the recursive query?

Thanks
--Harvinder

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Niall Litchfield
Oracle DBA
http://www.orawin.info

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http://www.freelists.org/webpage/oracle-l Received on Mon Oct 16 2006 - 09:34:05 CDT