Re: Chain vs SetLL/ReadE

["Michael Ryan" <michaelrtr@xxxxxxxxx>]

Hmmm...I dunno what the rationale would be for that. The difference
that I can think of is a SETLL doesn't move data, so it's a 'lower
cost' opcode than a CHAIN. IOW, if you're just checking to see if a
record exists, use SETLL rather than CHAIN. Otherwise, if you want to
retrieve the data if it exists, use CHAIN. But...if you're reading
several records with the same (or almost the same) key, than
SETLL/READE may perform better.

On Tue, Sep 2, 2008 at 9:34 AM, Chandra Krieg <chandrak@xxxxxxxxxxxxxx> wrote:
> Hello all,
>
> I have been told that the preferred method of random record retrieval is to use the SetLL, then do a ReadE and check for the %EOF indicator.
>
> Why is this preferred over using a Chain with %found or even checking for %Equal on the SetLL before reading the file?  I have been told that the Chain doesn't do what I'm expecting it to but I've never had issues in the past.
>
> I have read the archive posts and found opinions on the subject but no concrete explenation as to why.  As with some of the posts I don't understand why you would want to readE the file if the SetLL didn't find an %equal match or why if you plan to read the file a chain isn't appropriate.
>
> I'm being told to use the following code instead of a Chain.
>
> SetLL (KeyFields) FIleName;
> ReadE (KeyFields FIleName;
> DoW Not %EOF(FIleName);
>        do my stuff
>        ReadE (KeyFields) FileName;
> EndDo;
>
> Any explanations would be helpful!
>
> TIA!
>
> Chandra Krieg
> i5 Programmer/Analyst
> RateWatch
> (P) 1.800.348.1831 ext 311
> (F) 1.920.568.1403
> www.rate-watch.com
>
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