RE: Remote Select opening transaction

From: Bobak, Mark <Mark.Bobak_at_il.proquest.com>
Date: Tue, 3 Apr 2007 09:16:29 -0400
Message-ID: <AA29A27627F842409E1D18FB19CDCF270BD0A72D@AABO-EXCHANGE02.bos.il.pqe>

No, Marc is correct. When you do a select across a database link, it initiates a distributed transaction. I believe this is to deal with two-phase commit, and to guarantee that Oracle can deal the implications of distributed transaction.  

One way to avoid this transaction being opened is to initiate a read only transaction.  

Here's a quick demo on 9.2.0.8:  

SQL> select vt.used_ublk from v$transaction vt, v$session vs where vs.sid =(select sid from v$mystat where rownum=1) and vs.taddr=vt.addr;  

no rows selected  

SQL> select * from dual_at_pqd <mailto:dual_at_pqd> ;  

D
-

X  

SQL> select vt.used_ublk from v$transaction vt, v$session vs where vs.sid =(select sid from v$mystat where rownum=1) and vs.taddr=vt.addr;  

 USED_UBLK

---

         1  

SQL> rollback;  

Rollback complete.  

SQL> set transaction read only;  

Transaction set.  

SQL> select vt.used_ublk from v$transaction vt, v$session vs where vs.sid =(select sid from v$mystat where rownum=1) and vs.taddr=vt.addr;  

no rows selected  

SQL> select * from dual_at_pqd <mailto:dual_at_pqd> ;  

D
-

X  

SQL> select vt.used_ublk from v$transaction vt, v$session vs where vs.sid =(select sid from v$mystat where rownum=1) and vs.taddr=vt.addr;  

no rows selected  

SQL> select * from v$version;  

BANNER

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Oracle9i Enterprise Edition Release 9.2.0.8.0 - 64bit Production PL/SQL Release 9.2.0.8.0 - Production
CORE 9.2.0.8.0 Production
TNS for Solaris: Version 9.2.0.8.0 - Production NLSRTL Version 9.2.0.8.0 - Production  

-Mark
 

--

Mark J. Bobak
Senior Oracle Architect
ProQuest/CSA

"There are 10 types of people in the world: Those who understand binary, and those who don't."  

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From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Kerber, Andrew W. Sent: Tuesday, April 03, 2007 8:25 AM
To: marc.demlenne_at_gmail.com; oracle-l_at_freelists.org Subject: RE: Remote Select opening transaction

Hi. I am pretty sure your information is incorrect. I have never seen a select across a db link open a transaction.  

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

From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Marc Demlenne Sent: Tuesday, April 03, 2007 7:08 AM
To: oracle-l_at_freelists.org
Subject: Remote Select opening transaction  

Hello,

In Oracle 8, when performing a select query on another database threw DB link, Oracle opens a transaction that could only be closed by commit or rollback. That could be harmful when developers are not aware of this and don't close transaction. (leading to ORA-01562.)

What is the reason of this behaviour ? Is there some docs / faq explaining this ?
Is this feature also common to later versions of Oracle ?

Thanks a lot for any piece of information given,

--

Marc

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http://www.freelists.org/webpage/oracle-l Received on Tue Apr 03 2007 - 08:16:29 CDT