RE: Sorting

A few years back, before SilverLake was announced, my employer at the
time needed to convert a very large file from one format to another.  It
was a critical enough project that I was supplied an S38 model 70 for my
personal use.  This resulted in many jokes about my having the world's
largest PC.

I tested FMTDTA, CPYF, and a simple program to read one file and write
to another.  The read and write program was substantially faster than
FMTDTA and CPYF.  I suspect, but can't prove, it would also be faster
than SQL.  

So, with the file size in question I'd be inclined to do the following.

1. Create a physical file to accept the converted data and key it if the
final order  required a sort.  I'd let the operating system take care of
the sorting.

2. Write a simple program to read the original file and output to the
new file.

3. Save the converted data to tape or CD.

4. Do whatever it is needs be done with the converted data.

5. Delete the converted file.


But this is just one person's opinion.



-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of rob@xxxxxxxxx
Sent: Wednesday, April 30, 2003 2:11 PM
To: Midrange Systems Technical Discussion
Subject: RE: Sorting


1)  I don't use FMTDTA a whole lot.  But I've read the articles.  Yes,
it 
can be faster, (at least at the time of the article), but you shouldn't 
notice it unless the file is quite sizable.

2)  CREATE VIEW shouldn't work for RGZPFM.  CREATE INDEX might.

3)  Whether or not creating an index is faster than just selecting the 
records you want may be based on a number of factors:
-  Is the volume of the data significant to where you'll notice
- If it's for a one shot deal, the overhead of creating the index, then 
accessing the data, might be just the same as just selecting the
records. 
However, if it's for repeated access then create the index.
- There is some maintenance cost to maintaining an index.  It's the old 
speed of maintenance versus speed of reporting argument, and when you'll

actually see the tradeoff.  Unlike CRTLF, CREATE INDEX does not have the

parameter "MAINT" for Access Path Maintenance.



Rob Berendt
-- 
"They that can give up essential liberty to obtain a little temporary 
safety deserve neither liberty nor safety." 
Benjamin Franklin 
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