Re: IBM DDS to DDL and native file structure to RDBMS table direction

[rob@xxxxxxxxx]

This has been hashed around a lot in this list.  Most people are either in 
one camp or the other and no amount of convincing will change their mind.

I)  Field reference files
Some believe that DDL doesn't allow this.  However they've been 
enlightened by some of the responses on this list.

II)  Can't combine a view and a join in DDL but in DDS you can have a key 
on a logical file (like an index) that also does field selection, etc that 
a view does.
Valid point, if your I/O is traditional I/O versus sql I/O.

III)  DDS can't combine everything into one like DDL can.  You need a 
program or something to do the ADDPFCST's etc.
However most DDSer's wouldn't use a constraint if they can get paid to 
manually code that logic into every program.

IV)  Where do you store the DDL?
Same place as the DDS; in QDDSSRC, you just use RUNSQLSTM versus CRTPF or 
CRTLF.

V)  In DDL you have to do a LABEL ON to get field text and column 
headings.
True, but you can combine that in the same source member:
create table...;
label on ...;

VI)  DDL will appeal to the new people coming to the system.
DDSer will say "We're supposed to learn something new - why not them, this 
time?"

VII)  In DDL you have to do a trick to first create a table, then rename 
the table to get a record format name different from the file name.
Certain HLL's require this for traditional I/O.  However in RPGLE there's 
an F spec keyword to rename a record format that's just as effective.

VIII)  In DDL you can define things like BLOB's etc.
A DDSer would rather see their 400 put out to pasture than to see it store 
multimedia.  Or will assume that a 400 shouldn't be doing this.

So, what do you think?  Put this into a FAQ?  Granted there's been some 
minor 'digs' but don't you think I've covered most of the arguments?

Rob Berendt
-- 
Group Dekko Services, LLC
Dept 01.073
PO Box 2000
Dock 108
6928N 400E
Kendallville, IN 46755
http://www.dekko.com





"Dave Odom" <Dave.Odom@xxxxxxxxxxxx> 
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IBM DDS to DDL and native file structure to RDBMS table direction






I'm curious to know how many iSeries shops have heard the following and
will be heeding IBM's "nudging" and making the moves as described
below:

I went to a local iSeries user group meeting yesterday and an IBMer
from Rochester gave a presentation about IBMs direction concerning DDS
vs. DDL and ways to migrate from the current native flat file,
keyed-sequence file structure created by DDS to RDBMS tables created by
DDL.   He said that IBM's direction, and where their money is being
spent, is on SQL enhancements and not to DDS when it comes to data
structure definition.  The same is true for data access and manipulation
vis-a-vis SQL Data Manipulation Language (DML) vs. native READs, WRITEs,
CHAINS, etc.  In addition, the jest was that customers should make plans
to move both their data structure definition and application functions
to an SQL oriented world and away from, for the most part, the native
methodologies that have been around since S/38 days. 

I happen to think many of the presenters words were wise so the iSeries
may be seen by customer senior mangers(those that pay the bills) as a
modern platform that is "with it" and that can complete with other
platforms and database engines as companies look to the future and
create strategic directions.   He offered a "step-wise" approach for
those applications that were pretty static as far as enhancements were
concerned but advised any new applications and data structures be
designed and implemented using the new "way, truth and light".    As the
iSeries has Unix variants and Oracle or PCs and SQL Server or Oracle
biting at its heels, and many new function apps are being designed for
Microsoft operating systems or Linux or Unix, it seems like a wise move
and one that can show the iSeries engine can be a major player
especially now that you can have LPARs which can run OS/400, Linux and
AIX.   It also seems wise for the technical folks as skills in SQL and
true RDBMS data architecture are the way to go out there if you are
thinking about moving off the iSeries or your company mandates it. 

Since this presentation has been out for awhile, I may have missed your
reaction to it.  What do you and your companies think and plan to do? 
I'm curious for myself. 

Thanks in advance,

Dave Odom
Casa Grande, AZ 
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