NET/MASTER Network Control Language (NCL) Programmer's Guide

Displaying a Panel
Working With Panels
106160 Tandem Computers Incorporated 14–59
Displaying Panels on OCS
Windows
Any NCL process executing in the primary processing environment associated with an
Operator Control Services (OCS) window can execute the PANEL verb in an attempt
to take over the window and display a panel.
OCS always grants this bid for the display area if it is operating in its usual rolling
mode. It places the window in full-screen mode and queues any messages.
When the NCL process terminates or executes the PANELEND verb, the OCS window
reverts to its normal rolling mode and displays queued messages.
If the number of queued messages exceeds the size of the OCS window, the window is
automatically placed in autohold to ensure that you have time to read all messages.
While in full-screen mode, the screen cannot be horizontally split into a window with
less than four lines (this is the minimum size for an OCS window) or vertically split
into a window with less than eight columns. If you try such a split, the terminal alarm
sounds and an error message is displayed when the OCS window reappears.
NCL Process and OCS
Competing for an OCS
Window
If an NCL process executing in the primary processing environment associated with
an OCS window executes the PANEL verb while the OCS window is in its usual
rolling mode, OCS (the current owner of the window) always allows the panel to be
displayed.
If an NCL process attempts to issue a PANEL verb when the OCS window is in
HOLDING or AUTOHOLD ON mode, the PANEL verb is suspended. The OCS
window is placed into FS-HOLD mode. Operator input is required before the panel is
allowed to take over the window. At this stage, the OCS window is logically
considered to be in a CONTROL NOSHAREW condition. That is, OCS owns the
presentation area and is unable to release it.
Operator input releases the HOLDING or AUTOHOLD mode. At this point, OCS
immediately switches to the logical CONTROL SHAREW condition and allows the
panel to be displayed.
Multiple NCL Processes
Competing for an OCS
Window
Many NCL processes can execute concurrently in the primary processing environment
associated with an OCS window. Any NCL process in this environment can issue a
PANEL verb and attempt to display a panel on the OCS window.
At all times there is a logical owner for the presentation area of a window. This is
usually OCS, but when an NCL process issues a successful PANEL verb it acquires
logical ownership of the window and OCS operates in the background.
The same applies for other environments in which NCL processes can operate. For
example, a User Services window is initially owned by the NCL process that invokes
the User Services option from the primary menu. If that NCL process executes other
NCL processes by using the START command, these other NCL processes may bid for
the window to display their own panels. This is called panel bidding.
Once an NCL process succeeds in becoming the (temporary) owner of a window, it
may indicate its willingness to give up its ownership by using the CONTROL
SHAREW verb.