Re: 5250 and un-do

On 16 December 2017 at 11:27, Booth Martin <booth@xxxxxxxxxxxx> wrote:

Commit and rollback, if I understand it, is one-shot deal. If you make 15
entries and then rollback you lose all 15 changes. If you commit, you lose
all rollbacks. This may well be wrong; my understanding of commit &
rollback is limited.

One can twist COMIT's arm to treat 15 updates to CUSTOMER as one
transaction, but that's not what it's for. COMIT is intended to group
updates across multiple files, like an invoice header and all the
child invoice detail rows. They either all make it to the database,
or none of them do. I proposed COMIT as a way of asking for more
information.

What business thing are you trying to do?

The business thing is a subfile of data, say 4 columns, all can be changed,
deleted, or even added.

With deep respect, a subfile is not a business thing, it is a technology thing.

updated or not, I want to replicate the Ctrl-z behavior and be able to undo
changes, one at a time, for, say, 15 changes or until start of the session.

My first thought is that I have to keep an array of changes and read them
back 1 at a time but this has got to be a wheel that is already invented?
The rest of the world has had repeat un-do for 30+ years.

Yes, and they've done it with buffers. An array is one way to
implement that idea.

Jon's answer is exactly where I was trying to go. Are you looking to
build Lotus 1-2-3, 5250 Edition, where a user loads up a subfile,
works on it 'locally' (ie only her job can see the effects), adding,
changing, deleting, watching totals and interactions, and when finally
satisfied, returns the subfile back to the 'public' database? IMO
this is a poor fit with RPG. Between block mode I/O and an all too
finite screen size, and the fact that spreadsheets have been used by
the rest of the world for 30+ years, it just seems... like I don't
understand what the business thing is. If it's really a spreadsheety
thing, make it easier to download and upload the spreadsheet and let
the end user use her favourite spreadsheet program.
--buck