Re: CHAIN vs. SETLL (was Re: DOW vs DOU)

[Dave Mahadevan <mahadevan@xxxxxxxx>]

Steven Easton Mail wrote:
> 
> Even on the early models of the AS400, the chain with a PARTIAL key did not
> work exactly the same as the SETLL.  The chain would use any record that
> matched the search criteria depending on what was in the unspecified fields
> & RRN.  This same bug was found in early releases of the SETLL function on
> the S/38.  You could get around it by specifying all key field on either
> command if the file was unique keyed.  Unspecified key fields were not set
> to low values before the chain.  Yes, some times I still code around old
> bugs like this, and I occasionally  set off indicators before I do a read
> equal.  Remember that the record number is the last key of every indexed
> file.  Some files do not have a unique index.  Therefore the SETLL (early
> 38) and chain (38 & early 400) had problems with reading all records in
> these files.  If you can't trust a function to work all the time, don't use
> it all.  When you have been burned bad enough, you stay away from the fire.
>
I think the bug still exists on S/36 compatible RPG.  It caused me
headaches to figure this out. It was not pretty when users complained
that few checks for the client never showed up on the screen.   I even
complained to IBM.  Of course, "it was working as designed" was the
classic response.  The best way for non-unique key files is still READE
instead of CHAIN.  My personal preferance is a SETLL followed by a READ
in a DOW (let us not start that again).


-- 
Thank You.

Regards

Dave Mahadevan.. mailto:mahadevan@fuse.net
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