Devices (terminals, printers, plotters, etc.)
are subject to ownership. If a device is owned by a process, then
use of the device by other processes is restricted. For instance,
when a session owns a terminal, only the process which initiated
the session or its child process, can access the terminal.
To determine which process owns a device, use the MPE/iX SHOWDEV
command.
Asynchronous devices will be listed as one of the following:
Available. The device is not owned.
Any process that wants to claim ownership of the device can do so.
For terminals, this means that no one is logged on to the device
or no other process has programmatically opened the terminal. For
printers, it means that the device is not spooled,
nor has it been opened by a user program.
Unavailable. The device is owned. The owner—a
job,
a session,
or the system—is also listed.
Spooled. The device is owned by the spooler
while data is being transferred between a spoolfile
(on disk) and the device. Other processes can access the device
through the spooler, but only the spooler process owns the device.
Printers and plotters are the only asynchronous devices that are
spooled.
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 | NOTE: UPS devices are always owned by the system. |
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