RE: problem with duplicate records

What is done here is relying on chance to generate a correct reference
number. Time as a reference to an event, however precise you define it
to be, will always allow for situations where two events to happen at
the same time. It would have been much safer to use an unique
(sequential?) number to use as a key as you can ensure that there is
only one instance handing out the numbers, be it the system or a user
defined program or another method. You can still use time as a log-entry
mechanism, and in this case it would have logged the fact that two
archive entries have been made at the same time. Allowing a time as a
reference number is brittle architecture which has now proven this
point.

My two euro-cents,

Cor

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-
bounces@xxxxxxxxxxxx] On Behalf Of David FOXWELL
Sent: woensdag 19 november 2008 9:33
To: RPG programming on the AS400 / iSeries
Subject: problem with duplicate records

Hi,

Two users have managed to create the same archive reference number
while creating two different clients.

Like this :

ArchiveFile
Product1 Client1 RefNo1 10:41:57(time)
Product2 Client2 RefNo1 10:41:57

The program would crash if the problem occurred with the same product.
As it is 2 users in different services created the records at the same
time.

The user enters the client details and hits the enter key.
The program writes the client to the client file then calls an

external

procedure to find an unused archive number then write this number to
the archive file.

The client files look like this
Product1_clients
Client1 created at 10:41:53

Product2_clients
Client2 created at 10:41:56

I'm assuming that the creation of client1 took so long that the
creation of client2 caught up. The same time in the ArchiveFile is

just

a hazard.

I can think of ways to fix it, but I'd rather ask what are we doing
wrong?

Thanks.
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