[Info-vax] Orphaned processes on OpenVMS

[Snowshoe]

On 5/19/2011 6:10 PM, Johnny Billquist wrote:
> On 2011-05-19 14.53, Wendell wrote:
>> One of my biggest aggravations with *nix is the persistence of
>> orphaned processes. Say an app hangs. I log in to another virtual
>> terminal and "kill" it. That leaves various, no longer needed
>> processes still running, and the only way to really clean up is reboot
>> the system. At the worst, these stragglers can interfere with
>> restarting the app I had to kill.
>
> Huh? That's not exactly how it works. If you kill a process, all its
> children are transferred to the init process. They might keep running,
> though. But when they exit, init will reap them.
> If you explicitly want the children killed too, then I guess you just
> need to go through the process list, and kill them too.
> (Sometimes you can send signals to a whole process group, which might do
> what you want?)
>
>> 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?
>
> VMS don't have the concept of a hierarchy of processes in the same way
> Unix do. But you can kill processes in VMS, just as in Unix.

VMS does have subprocesses, and when you kill a main process, its 
subprocesses WILL die.  Subprocesses can have subprocesses as well.

Exceptions are if a process goes into a mwait state or something, 
usually meaning a bug in a driver or something.  In this case the main 
process won't go away (itself going into a mwait state) until if and 
when the subprocesses exit.

You can also create detached processes on VMS. In this case there is no 
relationship between the creator and createe after creation.  One dying 
doesn't affect the other.