[Info-vax] VMS internals design, was: Re: BASIC and AST routines

[Arne Vajhøj]

On 11/25/2021 5:07 PM, Arne Vajhøj wrote:
> On 11/25/2021 4:04 PM, Bill Gunshannon wrote:
>> On 11/25/21 2:20 PM, Arne Vajhøj wrote:
>>> Those running VMS today are mostly those without an easy way off
>>> VMS.
>>
>> I would really like to know what people could be running on
>> VMS on an Itanic that would be so difficult to move to a
>> totally different system.  Any applications are almost
>> guaranteed to be written in an HLL.  Just what is it that
>> they are doing on VMS that can not be done on another
>> system?
> 
> It can be done on another OS.
> 
> But the cost and risk migrating can be significant.
> 
> VMS specific language extensions, SYS$ and LIB$ calls,
> reliance on special features in Rdb or index-sequential
> files not available in other RDBMS or ISAM, huge amount
> of DCL scripts, Macro-32 pieces etc.etc..
> 
> A thousand easily solvable problems can when combined
> be a very problematic cost and risk (risk may very
> well be considered a bigger problem than cost).
> 
> It obviously depend on how the code is written. Some
> C or Cobol programs may be pretty easy to migrate.
> Most Pascal and Basic programs would be a rewrite from
> scratch to migrate.

The main reason that C programs are not ported off VMS
is probably that the authors went overboard with VMS
specifics instead of sticking to standard C.

I suspect that the main reason that Cobol programs are
not ported off VMS is that Cobol/VMS -> Cobol/Linux is
not considered good enough so that the migration is
Cobol/VMS -> X/Linux.

Arne