[Info-vax] Real live example...

[Denys Beauchemin]

On Monday, February 20, 2023 at 3:20:37 PM UTC-6, Denys Beauchemin wrote:
> On Monday, February 20, 2023 at 10:30:54 AM UTC-6, Arne Vajhøj wrote: 
> > On 2/20/2023 11:14 AM, Jan-Erik Söderholm wrote: 
> > > Den 2023-02-20 kl. 15:57, skrev Arne Vajhøj: 
> > >> For a Cobol/VMS application there are multiple options: 
> > >> 1) stay on Cobol/VMS 
> > >> 2) change both language and platform like to Java/Linux (*) 
> > >> 3) change just platform like to Cobol/Linux 
> > >> 4) change just language like to Java/VMS 
> > >> 
> >
> It has been our experience that changing the language of the application during a migration makes the whole migration project exponentially more difficult, expensive, long and risky. It makes the whole thing a moving target that is incredibly difficult to manage. One fun feature is that you’re always waiting for something to be migrated before you can run even just some parts of the application. Another fun feature is that testing is complex because of the differences between the two systems. 
> 
> Our long migration experience has confirmed that a tools-based, like for like approach is best. We have developed tools that transform the OpenVMS version of a language to a Linux-compatible version of the language, where such a language exists on Linux. We have a transformation tool for COBOL, another for Fortran, and yet others for C/C++. For languages that do not exist on Linux, such as Pascal, we have a translator that converts the Pascal to C++, and BASIC to C. 
> 

I wanted to add that we at Sector7 are very much adherents to the concept that if you can't measure it you can't manage it.  With a tools-based migration using our transformation engines, you get exact numbers of errors during the adjustment phase during each iteration.  Once the migrated code compiles cleanly on Linux and you build the executables, you have an exact number of executables to test and you can measure that.  Also, since the transformation is automated, you do not have to worry about encountering manual errors; when there is an error, it is systematic and you fix the tool.  The error is fixed throughout the code base.

The application will run immediately on Linux using the Sector7 library of system services running on Linux, so you do not have to wait for the rewrite of whatever VMS feature your application uses.  The whole migration is measurable and thus manageable.