RE: IBM i "Open I/O" Architecture

["Don" <dr2@xxxxxxxx>]

Scott...

Yeah, I guess I was thinking something more on the line of perhaps table
mapping or table field mapping, similar to how some of the conversion
utilities work...



-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx
[mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Scott Klement
Sent: Wednesday, October 21, 2009 4:35 PM
To: Midrange Systems Technical Discussion
Subject: Re: IBM i "Open I/O" Architecture

Hi Don,

RPG has a feature called "externally defined files".  When you declare 
an externally defined file, the RPG compiler reads the external 
definition of those files at compile-time, and generates variables in 
the RPG code that match the attributes of the columns (or "fields") in 
the file.

Since RPG is a compiled language, and the variables used in an RPG 
program must be established at compile-time, there's no way a run-time 
routine can query the structure of the database to fill in the column 
information.

The RPG compiler doesn't run your code at compile-time, so you can't 
write a handler that would fill-in the external definition at compile time.

If you wanted to use a solution that does NOT automatically generate 
variable names according to an external definition (such as a 
program-described file, or by calling SQL routines that return data into 
arbitrary variable names like my existing JDBCR4 srvpgm)  then you could 
indeed do what you describe...   but I don't think it'd work the way 
"regular" RPG programmers expect it to.


Don wrote:
> Hey Scott...
>
> Well, while we're looking at hypotheticals...why couldn't some API open a
> commlink to a target box with a non-DB2, but supported, DBMS on it.  Query
> the structure and engines, open the table desired, as desired, then use
SQL
> constructs to do I/O remotely and pass the items across in the same
concept
> that we use remote databases on the AS/400 now??
>
> DR2