Re: trigger program: can I fool a program into reading some selectfields from another file?

No you cannot do this with an OS/400 Read Trigger. Sorry, but IBM does not
allow
you to define a "before read" trigger, but only an "after read" trigger. So,
then, it is
"too late" and you cannot "alter" the data in the buffers.  (Well, you CAN,
but it will
have "no effect" on your application.)

There was a long debate about this (under "read trigger") on one of these
lists,
some months back...

----- Original Message -----
From: "Booth Martin" <Booth@xxxxxxxxxxxx>
To: <midrange-l@xxxxxxxxxxxx>
Sent: Monday, October 13, 2003 2:13 PM
Subject: Re: trigger program: can I fool a program into reading some
selectfields from another file?


> Yes you can. With a *BEFORE trigger. Chain to the new file, get the new
> value, and change the output buffer of the record.
>
> However it will change the output buffer every time, even after it has
> already been changed. I have the feeling I am missing something. Why not
> just change the data in original file and be done with it?
>
>
>
> ---------------------------------------------------------
> Booth Martin http://www.MartinVT.com
> Booth@xxxxxxxxxxxx
> ---------------------------------------------------------
>
> -------Original Message-------
>
> From: Midrange Systems Technical Discussion
> Date: Monday, October 13, 2003 2:45:40 PM
> To: 'Midrange Systems Technical Discussion'
> Subject: trigger program: can I fool a program into reading some select
> fields from another file?
>
> I have 1000+ programs reading a customer master file (the old cust file).
> Can I add a trigger program which performs the following:
>
> Whenever a program which reads a record from the old customer master file:
>
> Read a different new customer file, get the customer's address from the
new
> file, and place the new address field into the address field in the old
> customer record format.
>
> Using this method, I could add a new file and not have to change any of
the
> many programs using the old customer master file.
>
> If not a trigger program, is there any other method to accomplish this on
> the Iseries?
>
> I am aware of OVRDBF, but that will not allow me to grab select fields
from
> another file.
>
> Also I am familiar with OPNQRYF, but that would require CL changes and
would
> limit the ease of implementation. Also, OPNQRYF would not support any
logic
> built into the record retrieval.
>
> If I could use a trigger program, in theory, I could make a database
change
> which would require no changes to programs using the customer file.
>
> Thanks!
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