Re: Stopping a field on a file from being changed

[Charles Wilt <charles.wilt@xxxxxxxxx>]

Correct.

You want to use a BEFORE UPDATE trigger, then you just change the AFTER
value in the buffer.

Charles


On Thu, Feb 11, 2021 at 7:00 AM Alan Shore via MIDRANGE-L <
midrange-l@xxxxxxxxxxxxxxxxxx> wrote:

> Hi Rob
> Thanks for the info
> This shows that I didn’t know how triggers work
> You said that the trigger can modify the buffer BEFORE it hits the disk
> Does that mean, all I need to do is change the after value to be the same
> as the before value?
> There is no need to do another update of that record?
>
> Do you know of an example of what I need to do?
>
> Alan Shore
> Solutions Architect
> IT Supply Chain Execution
>
> [cid:image001.png@01D70054.4B79B800]
>
> 60 Orville Drive
> Bohemia, NY 11716
> Phone [O] : (631) 200-5019
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> E-mail : ASHORE@xxxxxxxxxxxxxxxxxxxx
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> Winston Churchill
>
> From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxxxxxxxx] On Behalf
> Of Rob Berendt
> Sent: Thursday, February 11, 2021 8:54 AM
> To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxxxxxxxx>
> Subject: [EXTERNAL] RE: Stopping a field on a file from being changed
>
> <snip>
> This should trigger a secondary update
> </snip>
> WRONG! It will NOT trigger a secondary update. You are changing the
> trigger buffer being passed to the row. See the ALWREPCHG on ADDPFTRG.
> You are updating the buffer being passed before it gets to disk. It only
> knows of the one update. "I think" the audit journal entry will only
> display the final results of the buffer. Which brings up some interesting
> questions on an audit.
>
> ProgramA does a WRITE or UPDATE to FILEA. FILEA has a trigger on it with
> ALWREPCHG set to yes. The name of the trigger is TRIGGERA. TRIGGERA can
> modify the buffer passed from PROGRAMA before it hits the disk. Or it could
> abort the write by issuing an exception message. If PROGRAMA does not have
> the appropriate error checking it will abort. Really hosed those programs
> which always assumed that any error on a WRITE was due to a duplicate key
> and automatically switched to an UPDATE instead (or generated a new key).
> Big reason why I'm not a fan of the MONMSG CPF0000 attitude
>
> Rob Berendt
> --
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>
> -----Original Message-----
> From: MIDRANGE-L <midrange-l-bounces@xxxxxxxxxxxxxxxxxx<mailto:
> midrange-l-bounces@xxxxxxxxxxxxxxxxxx>> On Behalf Of Alan Shore via
> MIDRANGE-L
> Sent: Thursday, February 11, 2021 8:20 AM
> To: midrange-l@xxxxxxxxxxxxxxxxxx<mailto:midrange-l@xxxxxxxxxxxxxxxxxx>
> Cc: Alan Shore <ashore@xxxxxxxx<mailto:ashore@xxxxxxxx>>
> Subject: Stopping a field on a file from being changed
>
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>
> Hi everyone
> We are on V7r3
> I have been asked if there is a way to stop a field from being changed
> (updated) - except on certain conditions
> I asked this question a while ago - and someone (forgive me - but I cannot
> remember who that was) suggested using a trigger
> I am wondering if this makes sense - any and all comments gratefully
> accepted
>
> Within the trigger program - on the file in question, on an update,
> compare the before and after values of that field
> If they are the same - let it go
> If they are different AND the conditions don't meet the exception
> conditions, update that record for that field ONLY within the trigger
> program back to the old value
> This should trigger a secondary update trigger - but because the program
> updating the record is the name of the trigger program - let it go
>
> If the conditions of the update meet the exception conditions - let it go
>
> I hope this makes sense
> As previously stated, any and all comments gratefully accepted
>
>
>
>
> Alan Shore
> Solutions Architect
> IT Supply Chain Execution
>
> [cid:image001.png@01D7004E.A31BDBC0]
>
> 60 Orville Drive
> Bohemia, NY 11716
> Phone [O] : (631) 200-5019
> Phone [C] : (631) 880-8640
> E-mail : ASHORE@xxxxxxxxxxxxxxxxxxxx<mailto:ASHORE@xxxxxxxxxxxxxxxxxxxx>
>
> 'If you're going through hell, keep going.'
> Winston Churchill
>
>
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