Re: E: Logical File or OPNQRYF or anyother way ?

Would a spoolfile be an example of a flat file on the iSeries? 
 
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Booth Martin
http://www.martinvt.com
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-------Original Message-------
 
From: Midrange Systems Technical Discussion
Date: 03/07/05 15:19:22
To: Midrange Systems Technical Discussion
Subject: Re: E: Logical File or OPNQRYF or anyother way ?
 
Hi, Dave
 
I don't understand why you say use the term "legacy AS/400 flat-file
architecture". I think there a misunderstanding here. A flat file, as I
understand it, is a file which has records in which there are no fields
(columns) defined. (And in some systems I suppose they might not even have
the same record length.) That is what was used with early forms of RPG - and
you COULD do it now - with I-specifications & O-specifications, where you
define the layout of the data internally to the program. But that was not
how it worked and works with what are called externally-defined files. Yes,
there WAS a flat-file architecture in the System 36 - and I'm probably even
a little wrong there. But there have been the equivalent of tables and
indexes and all you mention since the '80s on the System 38. The 400 uses
the same system and database architecture as the 38. The last time I
actually USED what i think you would call a flat file in RPG was 15 years
ago, in school, learning RPG II.
 
There is essentially no difference between the database on the i5 and that
on the 38 - except for some things like triggers and referential integrity
that were added more recently, at the time this "no-name" relational
database got the same name as its IBM brethren. But the lack of those items
did not make the database into flat-files.
 
There are charts that describe how SQL objects are implemented on the 400 -
tables are physical files, albeit with some different attributes. Indexes
and views are both logical files, inheriting all the general attributes
thereof and adding the attributes that distinguish them. (This, BTW, is the
beauty of the object-based architecture of this system.) A collection is
nothing more than a library. Old fogies know of rows as records and columns
as fields.
 
So there have ALWAYS been tables and appropriate indexes & views. We've even
had keyed physical files all along, which are sort of like having a primary
key, except they did not need to be unique, which disqualifies them for that
role.
 
Should we use Static SQL? Maybe, although native programs called as stored
procedures often provide better performance.
 
Now, I CAN create what looks like a flat file - CRTPF SOMELIB/SOMEFILE
RCDLEN(132) will do it. But this is usually a very special case. I use that
kind of thing for the output of a CPYSPLF command.Usually a file is created
either using DDS or an SQL CREATE statement.
 
Just for fun, create a DDS source member with a variety of data types - A25,
S5,0, say. Create the PF from it. Then use an equivalent CREATE TABLE
(CHAR(25) NOT NULL WITH DEFAULT,DECIMAL(5,0) NOT NULL WITH DEFAULT). Then
execute DSPFD and DSPFFD against the 2 objects - they are very close - a
couple little differences in attributes, but both can be accessed equally
well using SQL or native I/O.
 
Create a view - it is a logical file that is essentially a container for the
SELECT statement that will be run dynamically when you access that view. And
the view can be used in an RPG just like a good old logical file. Create an
index with SQL and an equivalent LF with DDS - again, DSPFD will show that
there is an access path in both, and they will look almost identical.
 
I guess you pushed my OK button - sorry to wax wordy - I'm sure I
misunderstand what you mean by a flat file, so please describe what that is
from your experience.
 
Thanks
Vern