RE: Remote Select opening transaction

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@pqd <mailto:dual@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@pqd <mailto:dual@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
----------------------------------------------------------------
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." 

 

________________________________

From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Kerber, Andrew W.
Sent: Tuesday, April 03, 2007 8:25 AM
To: marc.demlenne@xxxxxxxxx; oracle-l@xxxxxxxxxxxxx
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@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Marc Demlenne
Sent: Tuesday, April 03, 2007 7:08 AM
To: oracle-l@xxxxxxxxxxxxx
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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