Re: multiple trigger programs for many data files - is there a better methodology?

This is a great comment by Rob.

Is this the same project you posted about yesterday: the one where you are
to use ETL nightly to prepare data for BizTalk? Several others have
already commented (including myself) that triggers are not an ideal
approach in this scenario.
I understand you may just _want_ to write it yourself, or don't have
budget for a tool... but there is software available that could accomplish
this task in just a few hours, rather than a couple weeks of coding and
testing. Just saying.


Kind Regards
Alan Jordan

RODIN by Coglin Mill | 507.282.4151 x 103 | 507.261.4495 Mobile |
Rochester, Minnesota USA | www.thinkrodin.com




From: rob@xxxxxxxxx
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>,
Date: 06/12/2012 02:13 PM
Subject: Re: multiple trigger programs for many data files - is
there a better methodology?
Sent by: midrange-l-bounces@xxxxxxxxxxxx



Have you written a trigger program, or read the documentation on trigger
programs?

Think about this. You say perhaps you just want file name and keys. When

you declare a program as a trigger program it automatically receives
certain parameters when the trigger is activated. Among them are the
table name, a before image and an after image. An externally defined data

structure does a fine job of mapping the before image and the after image.

The trick is using one program to figure out the keys for 20 different
files. Do they have the same layout? I don't use a mediator. I do not
believe a mediator would simplify this. I do think that if you are early
on in the process it may help you implement new versions of the trigger
program until you iron out the bugs. A mediator basically would read the
table and say if I am monitoring this table then use this program to
process it and pass all the parameters again. You still have to determine

what columns are the keys for that table and where to record that.

That is if you want to process the data later. After all, you already
have the data that was changed. You could use the trigger program to just

output the 'after' image to a table. Imagine this layout:
- Table
- Timestamp
- Add/Change/Delete
- 'After' image

The problem with that is how do you sort that by Table, 'keys' and then
timestamp descending (to find the last update to a particular key).



Rob Berendt