Re: problem with duplicate records

[Wayne McAlpine <wayne.mcalpine@xxxxxxxxxxxxxxxxx>]

Typically you would use a data area to contain the next available 
number.  Your program retrieves the data area and locks it, then 
calculates the next sequential number and outputs it to the data area, 
then unlocks it.  It's simple and effective.

David FOXWELL wrote:
> Sorry, the contents of my file are misleading. The time isn't part of the reference number.
>
> ArchiveFile
> Product     Client     Ref    Time
> Product1    Client1    RefNo1 10:41:57
> Product2    Client2    RefNo1 10:41:57
>
>
> Summing up, 2 jobs writing to the same file. One job is quicker than the other. The first job calculates the data to write, tests to see it doesn't already exist and writes the data. In RPG, how should we prevent another job from doing the same and writing the same data before the first one?
>
>
> -----Message d'origine-----
> De : rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] De la part de David FOXWELL
> Envoyé : mercredi 19 novembre 2008 09:33
> À : RPG programming on the AS400 / iSeries
> Objet : 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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