Organising modules, programs and service programs

["Alan Campin" <Alan.Campin@xxxxxxxxxxxxxxxx>]

<snip>
I was thinking of creating two modules for each file in the database :
the first one would contain procedures to update, add or delete records
in the file, the second would contain procedures to get information from
the specified file (input only).  Finally, I thought of binding these
two modules in a service program.  So, I would have one service program
for all I/O's per file.
</snip>

Two thoughts on this. 

1. I am of the mind that things have moved past this point on the
AS/400. 

Specifically, I would be looking at using SQL rather than continuing to
use Record I/O. I know there have been a lot of back and forth on using
SQL vs Record I/O but I remain committed that SQL is where we should be
going. SQL just provides too many advantages. You are redoing the I/O
anyway. 

I thought about externalizing the SQL but in the end that didn't make
sense. 

Instead of externalizing the record I/O, look to using SQL. If you can
get to V5R4, the last really big impediment is eliminated, having to use
Fixed Format code for SQL. 

You might want to think more about externalizing business logic in
service programs and separating the view from the model. 

2. If you feel you have to stay with Record I/O, David Morris of Plum
Tree wrote a Data Mediator several years ago that is still the most
elegant solution to this problem. There is one mediator to make all
calls to and it calls the appropriate service program.  

I had worked on doing the same thing for several years and figured out a
better way to do it but in the end, I went to SQL.