Home » RDBMS Server » Server Administration » Can Oracle always guarrantee the data consistent in a distributed transaction? (11gr2)
icon4.gif  Can Oracle always guarrantee the data consistent in a distributed transaction? [message #581013] Sun, 31 March 2013 10:48 Go to next message
alantany
Messages: 115
Registered: July 2007
Senior Member

Hi,
I have a question about Oracle distributed transaction.
I have read almost all docs about distributed transaction on tahihi.oracle.com website,But I can find a statment about this:
Can Oracle always guarrantee the data consistent in a distributed transaction?
For example,there is a distributed transaction on node a,node b and nod c.
node b and node c informed node a they were prepared,
so node a committed,and inform node b and node c commit.
then node b committed and feedback,but network on node c broken at this point,So node a can't not get feedback from node c,but node a and node b has been committed, so what will Oracle do in this condition?
If node c rollback the data on local node, consistent in this distributed transaction was failed ,yes?

Could someone please give some explanation on this and tell if this statement is true?
Can Oracle always guarrantee the data consistent in a distributed transaction?

Thank you very much!
alan
Re: Can Oracle always guarrantee the data consistent in a distributed transaction? [message #581014 is a reply to message #581013] Sun, 31 March 2013 11:23 Go to previous messageGo to next message
Littlefoot
Messages: 19289
Registered: June 2005
Location: Croatia, Europe
Senior Member
Account Moderator
How a Distributed Transaction Commits says (note "commit point site"):Oracle

A distributed transaction is considered committed after all non-commit-point sites are prepared, and the transaction has been actually committed at the commit point site. The redo log at the commit point site is updated as soon as the distributed transaction is committed at this node.

Because the commit point log contains a record of the commit, the transaction is considered committed even though some participating nodes may still be only in the prepared state and the transaction not yet actually committed at these nodes. In the same way, a distributed transaction is considered not committed if the commit has not been logged at the commit point site.

If you're in doubt, see How to Handle In-Doubt Transactions.
Re: Can Oracle always guarrantee the data consistent in a distributed transaction? [message #581017 is a reply to message #581014] Sun, 31 March 2013 13:04 Go to previous messageGo to next message
Michel Cadot
Messages: 58477
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
So, in short, the answer is no. Wink

Regards
Michel
Re: Can Oracle always guarrantee the data consistent in a distributed transaction? [message #581034 is a reply to message #581017] Mon, 01 April 2013 02:16 Go to previous messageGo to next message
alantany
Messages: 115
Registered: July 2007
Senior Member

Thanks,Michel.
The Oracle doc says Oracle will recover the failed transaction automatically,
So can this guarantee the consistency?
Regards,
Alan
Re: Can Oracle always guarrantee the data consistent in a distributed transaction? [message #581040 is a reply to message #581034] Mon, 01 April 2013 03:57 Go to previous messageGo to next message
Michel Cadot
Messages: 58477
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
Read the links Littlefoot provided you.
There are cases where Oracle can't know how the transaction has to be ended (it is in-doubt) and in these cases the DBA has to force the end.
In the meantime, the global consistency (consistency across all the interested databases) is not guaranteed. So the DBA has to resolve theses cases as far as possible.
Of course, the consistency inside each database is guaranteed.

Regards
Michel
Re: Can Oracle always guarrantee the data consistent in a distributed transaction? [message #581057 is a reply to message #581040] Mon, 01 April 2013 06:35 Go to previous message
alantany
Messages: 115
Registered: July 2007
Senior Member

Thank you very much,Michel !

I think I am clear now!


Regards

Alan
Previous Topic: Oracle Ocfs2 not working in Oracle enterprice linux 6.2
Next Topic: ORA-03001: unimplemented feature
Goto Forum:
  


Current Time: Tue Jul 22 02:58:29 CDT 2014

Total time taken to generate the page: 0.07890 seconds