[Info-vax] Orphaned processes on OpenVMS

[Johnny Billquist]

On 2011-05-20 14.27, Wendell wrote:
> On May 20, 10:07 am, moro... at world.std.spaamtrap.com (Michael Moroney)
> wrote:
>> Johnny Billquist<b... at softjar.se>  writes:
>>> On 2011-05-19 16.47, Snowshoe wrote:
>>>> On 5/19/2011 6:10 PM, Johnny Billquist wrote:
>>>>> On 2011-05-19 14.53, Wendell wrote:
>> ...
>>>>>> I've heard it said that OpenVMS doesn't have this problem at all. How
>>>>>> does it prevent orphans or at least allow cleanup without rebooting?
>>
>> Yes the process hierarchy is quite different.  Unix has a single tree
>> while VMS has many parallel trees, most of which consist of a single
>> (detached) process.  The difference is, and this is what the original
>> poster was asking about, if a VMS process has subprocesses, the
>> subprocesses will be stopped unconditionally when the main processes
>> is stopped. The process is recursive; if the subprocesses have lower
>> subprocesses, they will be stopped first.  In Unix, they are not stopped,
>> but they become owned by the process above it or become orphan
>> processes.
>
> The VMS way sounds much more sensible. As I remember, VMS actually
> came after Unix. Anyone know if the design of the VMS process
> hierarchy was a deliberate reaction to issues with Unix?

Yes, VMS is newer. But no, I don't think Unix had much, if any, 
influence on design decisions in VMS. Maybe MULTICS did have some 
effect, but I wouldn't bet on it. When VMS was bring developed, Unix was 
still somewhat obscure, and only used to some extent in the academic 
world, and still a bit primitive by todays standards. (We're talking 
1975 here.)

VMS inherited a lot of concepts from RSX, but with regards to the 
process concept, RSX is rather different. I'd guess maybe TOPS-20 might 
have been a source of inspiration perhaps. Or actually maybe rather 
TENEX. Other OSes at the time that might have been inspirations could 
have been ITS. Not sure if WAITS had something similar as well.

	Johnny