Updating Numeric DTAARA in RPGLE

Numeric Data Areas are a little trickier than Alphameric

Updating any numeric DTAARA in RPGLE is slightly different in RPG /FREEFORMAT than in the good old fashioned column based RPG/400. Using RPG ILE, data structures are treated as mixed-character data. The subfields making up a data structure can be a mix of all data types: The nature of a data area is that it’s a string of data that can contain a mixture of various data formats.

If we play with the local data area (*LDA) its essentially a long string of stuff:

Of course this string of data can be populated with a mixture of values:

So, what do we do to update a numeric only data area?

The answer is simple – define a data structure with one numeric field in it and use that field.

Read a simple Nine Character Numeric Data Area

Updating a Numeric Data Structure in RPG/FREE

Let’s stop my waffle and look at an example. That is why you are here after all.

I have a numeric DS called EMLRECNUM, cunningly designed to hold an increment count of the number of emails floated out into the ether.

A common error example

We can define a Data Structure like this, and it looks correct:

 dcl-ds EmlRecNum dtaara('EMLRECNUM') qualified;     
    count zoned(9:0);                                 
 end-ds ;    

and when I try to update it like this:

 in *lock EmlRecNum;       
 emlrecnum.count += 1;           
 out EmlRecNum;     

Most annoyingly it all compiles and looks/feels like a jolly simple peace of RPG code.

But when you run it… oh boy... big wet explosion follows:

How do we fix this?

The problem is the difference between types of numeric field. Essentially – by default numeric values are packed when stored in IBM i, and when they are unpacked, they are called zoned. So, my previous example i defined it as zoned, so RPG was completely happy, but when I run the program it reads in a packed data structure and SPLATTER

So, I like to simply define the data area as a single field which is packed. The RPG Program will handle unpacking and using the field as we touch it.

If the only thing in the DTAARA is a *DEC value, use a stand-a-lone field rather than a data structure:

dcl-s EmlRecNum packed(9:0) dtaara('EMLRECNUM'); 

We treat the update in the exact same way:

in *lock EmlRecNum;
   emlrecnum += 1;
out EmlRecNum;

And thats that.

This little zoned/packed problem made me scratch my head for waaay too long. I hope it helps some other propellor headed IBM-i programmer type chaps or chappettes or transchapperoons out there 🙂