RE: DDS modernization - use of REFFLD

Years ago, the 2+4 field-naming convention was a great way to avoid
problems caused by accidentally overlaying the contents of similarly-named
fields in RPGII. The theory being that the programmer had to specifically
use a MOVE statement to populate an output field. This technique _reduced_
the possibility that a maintenance programmer would, at some later date,
accidentally trash the contents of NAME by chaining to CUSMAS, not realizing
that NAME also held the item-name. Programming techniques and RPG's
capabilities have changed but database column names haven't necessarily been
altered.

What I'm gathering is that DDL simply does not address the concept of
REFFLD. There exist techniques to simulate it, but the concept of REFFLD
wasn't a part of ASNI SQL and DDL won't support it either. One could even
argue that REFFLD is more of a 'data dictionary' concept than a 'Structured
Query Language' concept and that there are 3rd-party utilities available if
your shop needs that capability.

Fair enough.

JK

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-
bounces@xxxxxxxxxxxx] On Behalf Of rob@xxxxxxxxx
Sent: Friday, February 29, 2008 11:57 AM
To: Midrange Systems Technical Discussion
Subject: Re: DDS modernization - use of REFFLD

Here's the rub. Many people still name their fields based on the file
they are in. For example, if I have a field called ITEMNUM in FILEA and
FILEB they will call it AITEMNUM in one and BITEMNUM in the other. Rather
silly. Especially with prefix, or qualified, now if you are concerned
about field name collisions. Even prior to prefix I've seen system i
vendors who named the field the same. Naming it the same would allow you
to:
SELECT SYSTEM_COLUMN_NAME, SYSTEM_TABLE_NAME, SYSTEM_TABLE_SCHEMA
FROM syscolumns
WHERE SYSTEM_COLUMN_NAME='ITEMNUM'

I suppose you could alter this to
SELECT SYSTEM_COLUMN_NAME, SYSTEM_TABLE_NAME, SYSTEM_TABLE_SCHEMA
FROM syscolumns
WHERE SYSTEM_COLUMN_NAME like('%ITEMNUM')

You still can do the DSPFFD on printer and display files. There's
currently no plans to convert that to DDL that I am aware of.

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

"JK" <johnking@xxxxxxx>
Sent by: midrange-l-bounces@xxxxxxxxxxxx
02/29/2008 12:43 PM
Please respond to
Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxx>
Subject DDS modernization - use of REFFLD

All,

Yesterday I received a change request that requires an existing PF field
to
be increased in size. The actual program changes are trivial - the main
effort will be to identify which display files and printer files use that
field and verify that no other information will be overlaid by the new,
longer field.

Even if we didn't have a cross-reference utility, in our DDS-defined
system
this would be fairly simple - dump the DSPFFD to an outfile and query for
the appropriate REFFLD.

Without a utility, I'm not sure how you'd do the equivalent task in a
DDL-defined system. Query the column-label or column-text and hope that
the designer specified everything consistently?

This is not intended as a criticism of DDL, I'm only trying to understand
how you DDL-guys tackle situations like this. If we end up redefining
everything in DDL, what other things should we watch out for?

Many thanks, JK