Re: Use DTAQ unter Commitment Control to implement Acknowledgement

Hmmm... how would that work? The receiver doesn't know what is
coming unless it is looking for a response to a specific query. So Keyed
data queues won't really work, or will not scale at all. The problem with
reading a message an leaving it on the queue when you have multiple
receivers is that each receiver is independent, and does not know if
another receiver has read a given message. It could conceivably keep track
of the messages it has read, and only remove the message once it is
successfully processed, but that leaves some time for another receiver to
retrieve the message and process it again. the only way for keyed data
queues to solve this would be for the sender to direct the message to a
specific receiver, but in a dynamic environment, it is not really possible
(without a lot more handshaking) for the sender to know which receivers
will be available when it's message finally get to the head of the queue.
This can also cause load balancing issues if some messages take longer to
process than others.

On Thu, Sep 26, 2019 at 9:33 AM <midrangel@xxxxxxxxxxxxxxxxx> wrote:

You can if you use Keyed Queues.

-----Original Message-----
From: RPG400-L <rpg400-l-bounces@xxxxxxxxxxxxxxxxxx> On Behalf Of Mark
Murphy
Sent: Thursday, September 26, 2019 8:20 AM
To: RPG programming on IBM i <rpg400-l@xxxxxxxxxxxxxxxxxx>
Subject: Re: Use DTAQ unter Commitment Control to implement Acknowledgement

Except you can't scale it to multiple receivers.

On Tue, Sep 24, 2019 at 10:26 AM Voris, John <john.voris@xxxxxxxxxxxxx>
wrote:

This is how we wrote a system to process Payroll Clocks.
It is not complex and works like a charm without any complications.

Is there a way to rollback the receiving of a mesage from a dtaq in
case the processing of the message leads to an error. Like the
concept of acknowledgement on other messaging systems.

You can call QRCVDTAQ but not remove the message from the queue.

If there is an error, just leave the entry on the queue.
If there is no error then call QRCVDTAQ again and remove the entry.

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