Recently we had a small issue in our office with a program not providing the expected results when a case statement was created to see if the timestamp was entered or not.
Here is a sample program that I mocked up in another model to demonstrate the point.
The example below is a simple EEF (Execute External Function) that compares a couple of timestamp fields. The first LCL.Lee's Timestamp is initialised with a value of JOB.*System timestamp. In the second part field LCL.Lee's Timestamp 2 is left uninitialised so this will be NULL so in synon 2E terms that means '0001-01-01-00.00.00.000000'.
As one field is initialised and the other isn't you expect that the code to be performed will generate two messages in the joblog and these would say 'Timestamp is entered' and 'Timestamp not entered".
However, as you can see from below the messages are not as expected.
Let us take a little look as to the potential reasons why this has happened. First of all let's take a look at the generated code (RPG) for the comparison conditions.
As you can see these are pretty standard apart from the fact that they are comparing a CONSTANT value rather than a field or a hardcoded value like 'A' which you often see for status fields etc.
In our case we created a condition called 'Entered' for the timestamp field. We left it blank (upon creation) and 2E conveniently defaulted it to the NULL value '0001-01-01-00.00.00.00000'
The condition value is stored as a reference via file YCNDDTARFP. You will see that this condition references to another surrogate within 2E.
The clue is given in the source code snippet above where it refers to long constants. Taking a look at the file YCONDTARFP for 1003038 we see the value that is used by the source.
You can also see that this is 25 long in the file and as per the array declaration above.
Herein lies the issue.... The code is looking to compare the timestamp value vs a constant value. The timestamp field is 26 long and has 6 decimal places of precision for the millisecond element. If we place the program in debug and interrogate the value in LCL.Lee's Timestamp 2 we see that our field as below
But, this is being compared to below. These two are NOT the same.....
Now we understand the problem we need to consider how we can fix the issue. Fortunately there are several workarounds for this...
- Move the value (LCL.Lee's Timestamp 2) into a shorter field 25 long (truncating the last 0). We can then compare a 25 long field with a 25 long constant. As we are really only ever interested in EQ, NE, GT or LT comparison operators this will be okay.
- We can modify the source (highlighted above) to set the constant array to 25 and add a 0 to the CN value. But, we use a code generator so this is only recommended if you use source modifier programs and the pre-processor.
- Our chosen option was to NOT compare to a condition for 'Entered' or 'Not Entered' etc and instead compare to an empty field. We created a NULL Timestamp field and referred to its LCL context for a comparison (LCL so that it is always initialised within it function bounds) and not compromised like the WRK context.
The results are now as expected.
I've raised the issue with CA and expect a response soon. Perhaps it is fixed, or on a list. But considering it will mean a generator change and a file change for YCONDTARFP the workarounds above may be a better option so I hope that you all find this useful.
Thanks for reading.
Lee.
EDIT - I have heard from CA and the workaround option is the current recommend method. I agree with them that the scope and size of the change is quite high. Pick one of the three options above that works for your shop. Happy to hear if there are other options. LEe. 23/01/2017.
