Re: Use Trigger Program to Update Same File?

On Thu, 18 Sep 2003, Michael Naughton wrote:
>
> I have a file that has a numeric field that I want to use as a unique key
> -- like an auto-increment field, but we're still at V5R1 :-(. I thought I
> could do this with a trigger - simply set up a data area with the
> last-used number, add the trigger program before the insert, and it could
> read the data area, update the number, and put it in the field before the
> record is stored.

Yep, that's doable.

> This seemed simple enough, but I can't get it to work. I've got a trigger
> program, and I know it's running because I can see it in debug. I know
> it's finding the data area because the counter there is getting updated. I
> can even see in debug that the (new image of the ) field in the file is
> getting the new value. But it's not being stored in the file -- all the
> new records are showing up with zeros.

I hope you're not actually issuing an UPDATE op-code to that file in a
trigger program?  (That would cause the trigger to, basically, call
itself)


>
> Can this be done? If so, would someone give me a hint as to what I might
> be doing wrong and/or point me to somewhere where I can learn more about
> how this works?

I haven't done this since we did our Y2K conversion (at the time I was on
V3R2) so I'm a bit rusty, but this is what pops into my head:

  1)  the trigger must be a *BEFORE trigger.  Otherwise, the record is
        already written before your trigger gets called.

  2)  You must specify ALWREPCHG(*YES) when adding the trigger to the
        file, otherwise it will not allow the trigger to change the
        data.

  3)  You need to make your changes in the "after" buffer that's
        passed to you as a parm.  (don't use actual file op-codes
        in the trigger program)