RE: When is %EOF not an %EOF

["DeLong, Eric" <EDeLong@xxxxxxxxxxxxxxx>]

Thanks for the clarification, Hans.  I agree with you about coding for
correctness and maintainability, but please don't trivialize a 5 or 10
percent performance boost.  Sometimes that is all it takes to turn a
"failure" into a "success".  Also, while I don't doubt that there are many
factors that contribute to the perception that reade is a pig, I find it
very interesting that by simply changing a reade to a read and then testing
the keys manually can improve performance so dramatically. 

Regarding performance testing tools, what can I say.  I'm an RPG programmer
and I use whatever comes with the box, good bad or ugly.  ;)  

Eric DeLong
Sally Beauty Company
MIS-Project Manager (BSG)
940-898-7863 or ext. 1863



-----Original Message-----
From: Hans Boldt [mailto:boldt@xxxxxxxxxx]
Sent: Monday, September 29, 2003 9:03 AM
To: rpg400-l@xxxxxxxxxxxx
Subject: Re: When is %EOF not an %EOF


DeLong, Eric wrote:
> My understanding of this is the ReadE basically generates the same code as
a
> Chain.  Chain is a random I/O operator and will not allow record blocking
to
> occur.  There's a compiler info message about record blocking that
> disappears when you use ReadE on a file.
> 
> Eric DeLong
> Sally Beauty Company
> MIS-Project Manager (BSG)
> 940-898-7863 or ext. 1863
> 
> 
> 
> -----Original Message-----
> From: Christen, Duane J. [mailto:dchristen@xxxxxxxxxxxxx]
> Sent: Monday, September 29, 2003 7:58 AM
> To: 'RPG programming on the AS400 / iSeries'
> Subject: RE: When is %EOF not an %EOF
> 
> 
> Does someone have an explination of the performance difference? 
> I can understand that there would be a small performance hit with the
ReadE
> (< 5%) over Read but >10% just seems wrong.
> 
> Duane
> 


READE is different than CHAIN. There are two cases to consider: 
First, when a search argument is specified, READE is more or less 
equivalent to a sequential read followed by a comparison of the key 
of the record read to the search argument. Second, with Factor 1 
blank, or *KEY specified as search argument, a "get next key equal" 
request is sent to the database.

I won't comment on relative performance since it depends on a lot of 
different factors. If performance is important to you (more 
important than, say, program correctness or maintainability), you 
absolutely need to get intimately familiar with some good 
performance measurement tools. No amount of anecdotal evidence or 
hearsay can substitute for rigorous performance analysis using the 
proper tools.

Also, if you're quibbling over 5% or 10% differences, I would 
suggest your priorities are misplaced.

Cheers! Hans


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