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MQSeries.net Forum IndexWebSphere Message Broker SupportMemory Allocation - PROPAGATE

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Venkatpabolu
PostPosted: Thu May 02, 2013 8:27 pm Post subject: Memory Allocation - PROPAGATE Reply with quote

Newbie

Joined: 04 Mar 2013
Posts: 9

Hi,

I am going through a PDF that teaches ESQL coding... below pasted text is from that PDF. In case two when PROPAGATE DELETE NONE is issued, the next step is ' SET outputroot = inputroot', why should we again initialize outputroot ? My understanding is that outputroot still has data assigned in an instruction prior to PROPAGATE.

Case 1:

SET OutputRoot = InputRoot;
PROPAGATE; SET OutputRoot = InputRoot;
PROPAGATE TO TERMINAL Out1;
SET OutputRoot = InputRoot;
PROPAGATE TO LABEL ThirdCopy;

In the above example, the content of OutputRoot is reset before each PROPAGATE, because by default the node clears the output message buffer and reclaims the memory when the PROPAGATE statement completes. An alternative method is to instruct the node not to clear the output message on the first two PROPAGATE statements, so that the message is available for routing to the next destination. The code to do this iS:

Case 2 :

SET OutputRoot = InputRoot;
PROPAGATE DELETE NONE;
SET OutputRoot = InputRoot;
PROPAGATE TO TERMINAL Out1
DELETE NONE;
SET OutputRoot = InputRoot;
PROPAGATE TO LABEL ThirdCopy;

If you do not initialize the output buffer, an empty message is generated, and the message flow detects an error and throws an exception.

Can someone help me answer ?
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Esa
PostPosted: Thu May 02, 2013 11:13 pm Post subject: Reply with quote

Grand Master

Joined: 22 May 2008
Posts: 1370
Location: Finland

You are right. If the message is propagated with DELETE NONE, there is no need to copy the input message to OutputRoot again. On the contrary, depending on what is being done in the flow, in some rare cases it might be even harmful.
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Vitor
PostPosted: Fri May 03, 2013 5:42 am Post subject: Re: Memory Allocation - PROPAGATE Reply with quote

Grand High Poobah

Joined: 11 Nov 2005
Posts: 23814
Location: Ohio, USA

Venkatpabolu wrote:
I am going through a PDF that teaches ESQL coding.


What PDF? Sourced from where? Post a link.
_________________
Honesty is the best policy.
Insanity is the best defence.
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Esa
PostPosted: Fri May 03, 2013 7:38 am Post subject: Re: Memory Allocation - PROPAGATE Reply with quote

Grand Master

Joined: 22 May 2008
Posts: 1370
Location: Finland

Venkatpabolu wrote:

Can someone help me answer ?


Somebody has written a pdf for preparing for a certification test?
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mqjeff
PostPosted: Fri May 03, 2013 8:06 am Post subject: Reply with quote

Grand Master

Joined: 25 Jun 2008
Posts: 16683

You should copy InputRoot to OutputRoot when it makes sense.

If you don't know when it makes sense, then run experiments and read the documentation and think about what you read and think about the experiments.

It's easy to learn things using this simple technique.
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Esa
PostPosted: Fri May 03, 2013 11:32 am Post subject: Reply with quote

Grand Master

Joined: 22 May 2008
Posts: 1370
Location: Finland

mqjeff wrote:
You should copy InputRoot to OutputRoot when it makes sense.


Like when you need to modify it just a bit.

@Venkatpabolu:
Now here's the next exercise for you:

Would you believe that you can propagate InputRoot directly without having to copy it to OutputRoot?
Try to figure out how to do it!
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