RE: Expensive op codes

[Joel Fritz <JFritz@xxxxxxxxxxxxxxxx>]

I work in a shop that does a lot of mailing list processing that involves
files with between 1 and 8 million records.  Preparing a list involves a lot
of updates to the information that doesn't pertain to the name and address.
Our standard has been for many years sequential I/O writing the output to a
clone of the input file.  We generally use forced blocking with OVRDBF as
well.  I haven't benchmarked the process recently, but it seems to me that
two machines ago, sequential I/O made the process more than twice as fast.
Since the original file is ordered (not indexed) it allows comparisons with
other ordered files without using random I/0 by means of a simple linear
search.  The really scary thing is that reading all the records in two 2
million record files can be faster than reading all the records in one and
doing keyed lookup on the other.  

> -----Original Message-----
> From: Dave Murvin [mailto:davem@drme.com]
> Sent: Saturday, October 16, 1999 2:56 PM
> To: RPG400-L@midrange.com
> Subject: Re: Expensive op codes
> 
> 
>

/*                     Snip                                    */
> I have been doing some testing on record blocking and reading 
> of large files.
> Some of these tests may have been unscientific, but I think 
> they point the way to
> go.
> 
> All tests were run in batch on a dedicated S10.  Test jobs 
> were the only
> application running.
> File being read is a keyed logical with the physical file in 
> the same sequence as
> the key.
> Number of records in file is 1,027,600 with record length of  191
> 
> Both test runs used OVRDBF FILE(ECLL02) SEQONLY(*YES 341)
> Both test runs read the entire file by key.  Program 1 used 
> READE, program 2 used
> READ and compare.
> 
> Program 1 elapsed time was 33 minutes 38 seconds.
> Program 2 elapsed time was 12 minutes 38 seconds.
> 
> 
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