Who would have thought! I am starting to use RPG!

I have always said that I did not need to learn or use ‘RPG’ on the IBM i as I always found that ‘C’ could do all that I needed. Recently I was asked by a friend to help them with some RPG code to handle Java and the clean up of the objects it created (Java would not automatically clean up objects because they were effectively created by the RPG program and this program ran constantly, so temp storage just kept growing until it blew up). Not knowing RPG or understanding how the layout worked (I jumped straight into ‘/Free’!) I found this very difficult as ‘/Free’ is not really free format(there are still some column constraints) while ‘C’ really is free format. Still after some research and a lot of head scratching I finally got some sample code working, we then built a Service program that could handle the Java clean up and built code into the existing RPG programs to call it. The solution works the clients systems are not blowing up with memory issues caused by Java objects not being cleaned up.

I though OK that’s the last time I will have to do that and was happy that I could get back to good old ‘C’ programming. Unfortunately, I came across another issue which required me to pick up the RPG manuals and code up a test application.

We have a client who was experiencing problems with an application that uses commitment control and constraints that required us to build a test which would emulate the problem on our systems. As usual the first thing I did was to write a ‘C’ based solution, I did find a Commitment control test which was written by Paul Tuohy here. This was all written using RPG so I thought I would just follow the program logic and write a ‘C’ version which seemed the easiest option. While I could get the simple file update logic built and the program would work without Commitment Control, I found that as soon as Commitment Control was started the program would freeze on receipt of data from STDIN, (I will have to ask IBM why when I have time) so I decided my bets options was to take the code that Paul had provided and build my own interpretation of the program with some additional features I needed.

I wanted the program accept multiple entries plus allow deletes by key before the commit of the data so I had to make a few changes to the logic and add a new delete option. While the program is very clunky it does achieve what I needed it to do and I found out a lot about commitment control and constraints as a result. I am also unsure if the program is as efficient as it could be, but it works and for now that is all that’s needed.

Here is the code I ended up using.

H Option(*SrcStmt : *NoDebugIO) DftActGrp(*No) ActGrp('COMMITDEMO')
FHeader1 UF A E K Disk Commit(SomeTimes)
FDetails1 UF A E K Disk Commit(SomeTimes)

D Commit1 PR ExtPgm('COMMITRPG')
D SomeTimes n

D Commit1 PI
D SomeTimes n

D ToDo S 1a
D ToDel S 1a
D ToAdd S 1a
ToAdd = *Blanks;
Dow (ToAdd <> 'n');
Dsply 'Enter a Key Value (2 long): ' ' ' Key;
If (Key <> *Blanks);
Text = 'Header for ' + Key;
Write Header;
For Sequence = 1 to 3;
Text = 'Detail for ' + Key + ' ' + %Char(Sequence);
Write Details;
Chain Key Header1;
NumRows += 1;
Update Header;
NumRows = 0;
Key = *Blanks;
Dsply 'Enter a more Keys y/n : ' ' ' ToAdd;
ToDel = *Blanks;
Dsply 'Do you want to delete entries : ' ' ' ToDel;
Dow (ToDel <> 'n');
Key = *Blanks;
Dsply 'Enter the Key to Delete : ' ' ' Key;
if (Key <> *Blanks);
chain Key header1;
if %found;
delete header1;
ToDel = *Blanks;
Dsply 'Do you want to delete more entries : ' ' ' ToDel;
ToDo = *Blanks;
Dow (ToDo <> 'c' and ToDo <> 'r' and ToDo <> 'i');
Dsply 'c - Commit, r - Rollback, i - Ignore ' ' ' ToDo;

If SomeTimes and (ToDo = 'c');
ElseIf SomeTimes and (ToDo = 'r');

*InLR = *On;

Note: the Blog does not allow RPG code indentation so the view you see is not what it was copied in as!

The database was exactly the same that Paul had defined including the cascading delete for the details file (I liked that bit) so when we delete the Header Record the matching records in the Details file are also deleted. That saved us having to chain (see I can speak RPG) the details file and remove the entries. Now we can see the problem the client was experiencing and know how to resolve it.

As usual Google was our best friend, thanks to Paul Tuohy and ITJungle for providing the sample code we based the test application on. I am now a little less resistant to RPG and may delve a little more into its capabilities and how I can use it effectively, who knows I may even become good at it?? The point I am trying to make here is that while I still do not want to use RPG, I did what I keep telling others to do, I used the best tool for the job. Using any language just because it is all you know is not always the best option, sometimes you have to jump outside of your comfort zone and try something new.


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