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Message
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| svichare |
 Posted: Tue May 05, 2009 9:21 pm Post subject: Does XA Support For Oracle RAC |
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Newbie
Joined: 05 May 2009
Posts: 2
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We would like to know if there is XA Support for Oracle RAC.
We have configured tnsnames.ora as follows:
RACPELPROD =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = racvir1)(PORT = 1521))
(ADDRESS = (PROTOCOL = TCP)(HOST = racvir2)(PORT = 1521))
(LOAD_BALANCE = yes)
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = pelprod)
(FAILOVER_MODE =
(TYPE = SELECT)
(METHOD = BASIC)
(RETRIES = 180)
(DELAY = 5)
)
)
)
We have also configured our XA Open String as follows:
Oracle_XA+SqlNet=RACPELPROD+Acc=P/p6p4imp/p6p4impmanager+SesTm=35+threads=true+LogDir=C:\Temp
Our Applications go into reconnectivity if the Oracle Instance goes down. But with XA we expect that if a particular Instance goes down, Our application will switch to the other Instance in the RAC.
Thanks in Advance. |
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| Vitor |
| Posted: Tue May 05, 2009 11:51 pm Post subject: |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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Wouldn't this be better posted in a Oracle forum? 
The issue (surrounding a product I'd like to admit I have not even heard of) seems to be an XA transaction not being established when this thing fails over. I don't see the immediate connection to WMQ, except that the application in question may be using queuing.
_________________
Honesty is the best policy.
Insanity is the best defence. |
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| svichare |
| Posted: Wed May 06, 2009 1:51 am Post subject: XA Support for Oracle RAC |
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Newbie
Joined: 05 May 2009
Posts: 2
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Thanks for the update.
The product being used is IBM Websphere MQ 
Our understanding of XA-RAC interaction was that since the XA String which was specified pointed to an Oracle RAC set up, the switch-over from one Oracle instance to another in case of a breakdown sholud be handled by XA
Any help would be appreciated. |
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| Vitor |
| Posted: Wed May 06, 2009 2:10 am Post subject: Re: XA Support for Oracle RAC |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| svichare wrote: |
| The product being used is IBM Websphere MQ |
Ok, so you've got Oracle (under the control of this RAC gadget), WMQ, an application and A.N.Other piece of software doing XA coordination possibly. Got that. All of this participates in XA transactions. Got that.
| svichare wrote: |
| Our understanding of XA-RAC interaction was that since the XA String which was specified pointed to an Oracle RAC set up, the switch-over from one Oracle instance to another in case of a breakdown sholud be handled by XA |
Hence my point that a question about how Oracle RAC behaves in a given situation might be better posted in an Oracle forum. Which is not to say someone in here doesn't have a comment to make of course!
I still struggle (possibly because of my unfamiliarity with the product) with the idea that an XA transaction would in some way trigger failover. Or that WMQ would be anything but a participant in this transaction, rather than a mover in it.
Do I have the wrong end of the stick? Or the wrong stick entirely?
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| WMBDEV1 |
| Posted: Wed May 06, 2009 2:45 am Post subject: |
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Sentinel
Joined: 05 Mar 2009
Posts: 888
Location: UK
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| Quote: |
| the switch-over from one Oracle instance to another in case of a breakdown sholud be handled by XA |
I wouldnt say it was handled by XA per se. The Oracle client handles the "switch over".
From my experience when an Oracle node went down in the RAC the connection had to be re-established and the transaction was rolled back.
I'm not massively sure whether using XA or not will make any difference to the need to be re-establish the connection, but i'm not an Oracle expert.
Just out of interest what is your transaction manager? is it MQ, it looks like it might be, please confirm? |
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| fjb_saper |
| Posted: Wed May 06, 2009 3:09 am Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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I would not expect any transaction in flight to fail over. I would not expect any established connection to fail over. If the need arises to reestablish a connection then that connection fails over to the other node in the rac.
I know that this works well when using a J2EE server with a connection pool.
(see purge policy of the pool).
For MQ I am not so sure. I believe the connection to the DB is established at startup of the QM. So if that connection is broken may be you need to restart the qmgr? You may open a PMR with IBM about that... and I am sure they will give you the details on how to work with the Oracle RAC.
Have fun. 
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