Re: 5250 and un-do

We do use the same tecnique extensively through all our Db, whatever the
language used to develop our programs (native rpg or .net from our web
apps) and it works fine.

Il 20 dic 2017 9:07 PM, "Henrik Rützou" <hr@xxxxxxxxxxxx> ha scritto:

If you really want to know it, it's and old habbit that goes back to 1977 -
and if it isn't broken,
works well and suits the purpose - why try to fix it?

And even in 2017, where timestaming isn't enough any more (no ns support) -
it still works ;-)

On Wed, Dec 20, 2017 at 7:05 PM, Justin Taylor <JUSTIN@xxxxxxxxxxxxx> wrote:

" I like Henrik's idea of including an update counter in a record,"

Why not use the built-in Db2 functionality for this?



-----Original Message-----
From: Nathan Andelin [mailto:nandelin@xxxxxxxxx]
Sent: Tuesday, December 19, 2017 12:39 PM
To: RPG programming on the IBM i (AS/400 and iSeries) <
rpg400-l@xxxxxxxxxxxx>
Subject: Re: 5250 and un-do

Just to follow up on some of the comments so far. Good points all around
regarding database normalization.

I've never found any use for locking a record while it is displayed, given
a multi-user environment. I shake my head in awe.

I like Henrik's idea of including an update counter in a record, and
checking to see if it has changed since the current user last read the
record. That's more efficient and easier to implement than comparing
multiple record buffers in memory, each containing a copy of a record in a
different state.

For applications that are only required to update say one column in a row,
you end up needing a record buffer on the update operation that is
distinguished from the record buffer used in the read-from-screen
operation. Use an assignment statement to copy a column value from one
buffer to the other. An SQL Update statement does that, under the covers.

Though it would be possible, I wouldn't expect a super-basic utility like
DFU to have an undo key. Use cases for undo fall in the realm of
application development.

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Regards,
Henrik Rützou

http://powerEXT.org <http://powerext.org/>
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