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

Describing Asynchronous Devices
How Operation Modes Set Functionality
Chapter 9
161
How Operation Modes Set Functionality
Six device operation modes can be used. Each has different capabilities and is intended
for a specific purpose. The six are as follows:
•System console
• Session-accepting devices
• Programmatic devices
• Spooled devices
•Slaved devices
• Uninterruptible Power Supply (UPS) devices on the DTC.
System Console
On CIO systems, the system console is the only device that is not connected to the
computer through a DTC. The computer is aware of its existence from system
initialization. It is connected to a special interface card in the cabinet called the access
port.
Although the system console is session-accepting, it has the following added
functionality:
• Receipt of console messages. The system console is the message center for the
computer. Messages can be informational, such as notifying an operator when users
log on or off the host. Messages can also alert an operator to take an action, such as
mounting a magnetic tape on the tape drive so that its data can be accessed by a user
program.
• Execution of console commands requiring the console attention character. These
commands are called
[CTRL]-A
commands. Using
[CTRL]-A
, an operator can interrupt
an action on the system console to enter commands that will abort one or all users,
answer console requests, or shutdown the computer.
• Execution of other console commands. These commands are used for system startup
and shut down procedures.
Because the system console serves a specific purpose, the following functionality is not
provided:
• System console operation at 19200 bps. Supported speeds are 300, 1200, 2400, 4800,
and 9600 bps.
• User block mode applications. Only block mode applications that use VPLUS can run
on the system console. NMMGR is supported on the system console.
Block mode applications do not prevent the system console from printing received
messages. Such messages can cause data on block mode screens to be overwritten or
lost. Because of this, block mode applications should not be run on the console.
Some console functionality can be given to the logical console. The system console can
“pass” console functionality (except
[CTRL]-A
) to any other user; a user with system
manager capability can “grab” the console by issuing the CONSOLE command.