Configuring Systems for Terminals, Printers, and Other Serial Devices (32022-90057)

Describing Asynchronous Devices
How Devices Are Owned and Why
Chapter 9
159
How Devices Are Owned and Why
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.
NOTE UPS devices are always owned by the system.