• Subject: Re: Record selection when reading a big file
  • From: John Carr <74711.77@xxxxxxxxxxxxxx>
  • Date: 29 Jun 97 11:06:28 EDT



Date:   6/29/97  8:27 AM

RE:     Re:  Record selection when reading a big file

At 09:14 PM 6/28/97, you wrote:
>I'm not used to big machines and big files.  The box has V3R2 and I think
>may be an ?F60? (its bigger than their development box, which they keep
>referring to as a 45).  
>
>The file I am concerned with has 5 million records.  I want to go through
>this file making selections based upon choices made for several fields. 
>Normally I would use the RPG cycle and bang down through the file (no K),
>making the selection tests with the most limiting choice first, and as
>soon as a record fails, goto end of cycle.  Any record that tumbled
>through that series of tests would be written to a workfile, with a key
>field made up with the sort-choices as made on the selection screen. Over
>90% of the time the final work file will hold less that 10,000 records.
>
>I've done this a lot on smaller files and smaller machines.  It offers a
>real easy front-end for the user and is flexible.  
>
>But I have never done this on a 5 million record file.  Am I about to make
>a fool of myself? -- 

Booth,
As Al has said,  Try ANTHING else.  Try getting a small subset to "Play"
with.  Maybe 500,000 records.  Try various techniques on it. Time your
results.  

Do you have an index even close to what you need?  I personally do not like
Select/Omits in logical files. I have found that if you make the highest
key be what ever you were going to use as the "Select"  You can usually 
use that index in many more application needs.  For example if you were
going to say "select if CODEXX = 'B' in your logical. Make CODEXX a 
higher key in the logical. OPNQRYF, Query/400, SQL may use that index
many,many times for different values for CODEXX ('B', 'C', 'A' etc)

Do your major selects in the "Tool" like OPNQRYF then process the "Rare"
conditions maybe in the RPG.

John Carr
EdgeTech


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