Re: Possible timing issue with IO

[Jon Paris <jon.paris@xxxxxxxxxxxxxx>]

You need FEOD(N) to be sure of catching anything written by the program Vern.

There may also be an impact from different blocking in the two programs that update the file - but using FEOD should fix it. For sure use the (N) extender. FEOD without it is a performance pig.
 
On 2014-01-24, at 4:16 PM, Vernon Hamberg <vhamberg@xxxxxxxxxxxxxxx> wrote:

> Y'all
>
> I haven't had to deal with quirky IO issues in a long time, so here goes 
> with my problem - hope someone has seen this behavior.
>
> I have a program that reads through a file (let's call it VHFILE) from a 
> certain position and is checking for duplicates of a type - not 
> important - I'm using a state machine to handle this.
>
> When this program is called on its own, it finds the duplicates.
>
> When it is called from a program that just wrote to the file in 
> question, it rarely finds anything - but it does sometimes catch 1 or 2 
> instances of the problem.
>
> It seems that this new program doesn't see the data that was just written.
>
> VHFILE has 3 logicals - and VHFILE is quite large - one of what we call 
> our big files.
>
> VHFILE - arrival - 51million
> VHFILEA - 51million entries - 1.5GB
> VHFILEB - 51million entries - 1.8GB
> VHFILEC - 10million entries (S/O) - 420MB
>
> OK, here's more info on the call stack -
>
> 1. CLPGMA - OPM
>      calls
>      2. CLPGMB - OPM with simple OVRDBF on file in question
>           calls
>           3. RPGPGMA - ILE - *CALLER - uses VHFILEA as UF A (update + 
> add) and has deletes and writes
>                calls (after all writes are done - the number varies, )
>                4. CLPGMC - ILE - *DFTACTGRP
>                     calls
>                     5. RPGPGMB - ILE - QILE - uses VHFILEC as UF 
> (update only) and has only deletes
>
> There is no need of sharing ODPs.
>
> I recognize the "flaky" activation group structure, but I don't think it 
> should matter - in fact, it might help, to isolate opening VHFILEC from 
> the open of VHFILEA.
>
> No commitment control in place - there is iTera for replication or whatever.
>
> So -
>
> 1. Is FEOD a way to overcome this?
> 2. And is the N extender useful? RPG Reference says it can perform 
> better - unwritten records in a block are written to the database, 
> although not necessarily to disk (non-volatile storage).
>
> Or some other idea.
> Thanks
> Vern
> -- 
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Jon Paris

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