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  2. RPG400-L
  3. September 2003

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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