Re: Write a record at a specific RRN

You could pause the application of changes while doing the upgrade to the
backup server..

Once done you allow it to catch up and then switch to the updated system
while beginning the update on the original.

The HA software should be able to handle differences in the table...or at
least the adding and possibly extending of columns. "dropping, renaming,
complex conversions" are probably another story.

The OP is basically trying to roll his own "single system HA" anyway. And
apparently without an actual primary key defined on the table.

Charles





On Sun, Aug 15, 2021 at 4:59 PM Jim Oberholtzer <midrangel@xxxxxxxxxxxxxxxxx>
wrote:

Charles, while I agree with your sentiment, how is an HA system going
address the specific problem? Keeping in mind that the HA is usually
updated from the primary in some number of milliseconds.

Jim Oberholtzer
Agile Technology Architects

On Aug 15, 2021, at 5:33 PM, Charles Wilt <charles.wilt@xxxxxxxxx>

wrote:

My 0.02...

If you can't afford 5hrs of scheduled downtime periodically, then you
should have some sort of HA system.

Charles

On Fri, Aug 13, 2021 at 5:50 AM Paul Nicolay <paul.nicolay@xxxxxxxxxx>
wrote:

Maybe I should provide a bit more background on the reason for this
question (and the overriding system value) one.

The problem is that we need to change the structure (ie. this can be
anything from extending, adding, dropping, renaming, complex

conversions,

... of fields) of a huge (> 100 million records) table while operating

in a

24/7 environment.

Fact is that we even have multiple tables like that (that need to go in
one time) so the magnitude is even factor x. This means that we can't

end

all jobs, change the layout of the tables (this will take many hours),
promote the software and continue to work as it is downtime that should

be

avoided.

The idea (which is not mine) is therefore to replicate the existing
database table to a shadow version until everything is in sync (without

any

impact on the source tables), find a downtime spot, move the tables in

the

production environment, promote the software and continue working. This
method should limit the downtime to minutes instead of many hours.

While there are some tools that offers this... they have certain
limitations so I was looking if I could write a next-gen version of

them.

The recent questions are related to one technique I have in mind but

there

are others as well (all with pro and contra's).

The goal is also to find a solution that works with all current
capabilities a database has (unique keys, constraints, identity columns,
null values, ...).

________________________________________
From: RPG400-L <rpg400-l-bounces@xxxxxxxxxxxxxxxxxx> on behalf of John
Yeung <gallium.arsenide@xxxxxxxxx>
Sent: Thursday, August 12, 2021 21:47
To: RPG programming on IBM i
Subject: Re: Write a record at a specific RRN

If the "still in use and updated continuously" is a problem, yet it is
also "a temporary process", then... I think you still haven't
described the higher-level situation well enough.
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