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| Confusion: multiple syncpoints with a single MQCmit / MQBack |
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| pcelari |
 Posted: Mon Oct 09, 2006 5:40 am Post subject: Confusion: multiple syncpoints with a single MQCmit / MQBack |
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Chevalier
Joined: 31 Mar 2006
Posts: 411
Location: New York
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Want to clarify my last bit of confusion over syncpoint - cmit.
My program read from a queue, do a little manipulation in the msg, and put it into a second queue. My current setting is like this:
...
gmo.Options = MQGMO_SYNCPOINT;
MQGET()
...
pmo.Options = MQPMO_SYNCPOINT;
MQPUT1(...)
if(Reason == MQRC_NONE)
{
MQCMIT(Hcon, &CompCode, &Reason);
}
else
{
MQBACK(Hcon, &CompCode, &Reason);
}
As there is no generic sycpoint, I have to use one for get and another one for put, at different points in the code. the code seems to work. But I'm not so sure if it is correct.
So the question:
Is the use of mutiple syncpoints with a single commit/backout correct?
_________________
pcelari
-----------------------------------------
- a master of always being a newbie |
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| Nigelg |
| Posted: Mon Oct 09, 2006 5:46 am Post subject: |
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Grand Master
Joined: 02 Aug 2004
Posts: 1046
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Yes.
An MQCMIT (MQBACK) commits (backs out) all msgs put/got since the last MQCMIT. A qmgr connection only has a single unit of work (UoW), begun when the first msg is put or got in syncpoint, and ended when MQCMIT or MQBACK is called.
The use of the MQGMO_SYNCPOINT and MQPMO_SYNCPOINT is to do the get and put in the UoW. Without that option the msg would be got/put outside syncpoint, i.e. immediately, and neither could be backed out if the other failed.
In your case, the GET and PUT of the msg are in the same UoW, so either they both succeed or neither does.
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| zpat |
| Posted: Mon Oct 09, 2006 5:47 am Post subject: |
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Jedi Council
Joined: 19 May 2001
Posts: 5866
Location: UK
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The GMO and PMO SYNCPOINT options only start a new UoW if there is not one already in progress, otherwise they will join the current one.
You can't have two Units of Work on the same connection handle at the same time. All syncpointed operations will be under one U of W and they will all be commited or backed out at the same time. |
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| pcelari |
| Posted: Mon Oct 09, 2006 11:18 am Post subject: |
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Chevalier
Joined: 31 Mar 2006
Posts: 411
Location: New York
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Many thanks for the concise clarifications.
The manual seems to be less clear about this, or I haven't find it.
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pcelari
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