[Info-vax] Device with owner that doesn't exist.

[Michael Moroney]

"Fred. Zwarts" <F.Zwarts at KVI.nl> writes:

>Op 23.okt..2019 om 14:34 schreef Jan-Erik S?erholm:

>> I'm looking at it right now and I'll try to force this
>> hanging device scenario on our test box, of course. But
>> When it is really needed, is when work places in the
>> factory stands still and really need to get going.
>> 
>> And it must be possible to use it in the COM files that
>> the users can submit from there menu system.
>> 
>> Today, I simply change the appliation startup COM file
>> and assignes another unused TNA device number and let the
>> hanging one die by its onw. Actually, the device in my first
>> post above (TNA8883:) is gone now, a couple of hours later.
>> I changed the COM file to use TNA8884: instead so that they
>> get the printer online again and then left it like that.
>> And now TNA8883: is simply gone...
>> 
>> The TNA device points to an IP and port number of a label
>> pinter (Zebra). Sometimes when the printouts hangs, the users
>> simply close their session and that is where the user process
>> goes away and the TNA device gets hang, I guess.
>> 
>> I also have another idea where a pool of TNA numbers are used
>> in a round-robbin fashion. Then we can let any hanging devices
>> just go away by their own.
>> 
>> But I'll look at this first and we'll see...

>Maybe the device was being deleted, but was waiting for an IO operation 
>to complete. It might have been that after a TCP time-out, or when the 
>printer disconnected, this IO completed and the device was deleted.

The way this usually happens is when a normally nonsharable device (typically
a tape drive, but terminals are included) gets accessed by multiple users
with SHARE privilege, followed by a certain sequence of closes/deassigns.
The device remains allocated to a process which may no longer exist.

This, or something similar, has been a problem in VMS for decades.