Technical data

Managing Peripheral Devices
8.6 Managing Terminals
Virtual terminals are identified by the VTAn: device name. After the SYSGEN
or IOGEN command is entered, any terminal with the TT2$M_DISCONNECT
characteristic set prior to login is treated as a virtual terminal.
Note
LAT terminals (LTAn:) can be disconnected if the TT2$M_DISCONNECT
characteristic is set, but remote terminals (RTAn:) cannot be
disconnected.
You can set the TT2$M_DISCONNECT characteristic in one of two ways:
• Enable the feature on a systemwide basis by setting the appropriate bit
in the system parameter TTY_DEFCHAR2. You must use this method for
dynamically created terminal devices; for example, LTAn: devices.
• Enable the feature on a per-terminal basis by using the DCL command SET
TERMINAL/DISCONNECT.
Controlling the Use of Virtual Terminals
You can control the use of virtual terminal sessions in the following ways:
• In SYLOGIN, include a user-written DCL procedure that enforces a system-
wide or user-specific policy for the use of virtual terminals at your site.
• Specify the maximum number of detached processes that individual users
can create by specifying a value for the UAF resource limit MAXDETACH.
See the documentation of the MAXDETACH user quota in Table 7–9 for the
implications of using this quota, as well as information about how to set this
quota.
• Using the system parameter TTY_TIMEOUT, specify the length of time a
disconnected session remains before being logged out.
• Restrict the use of virtual terminals by enabling them on a per-terminal basis.
• Restrict individual users from being able to reconnect to disconnected
terminal sessions by specifying the UAF flag DISRECONNECT.
• Create a site-specific LGI callout module that provides the preferred policy at
your site. Information about LGI callouts is in the OpenVMS Utility Routines
Manual.
8.6.2.1 Using Virtual Terminals for Dynamic Asynchronous DECnet for OpenVMS (VAX Only)
Virtual terminals are required for dynamic asynchronous DECnet communication.
A dynamic asynchronous line differs from a static asynchronous line or other
DECnet line in that it is normally switched on for network use only for
the duration of a dialup connection between two nodes. Dynamic switching
of terminal lines to asynchronous DDCMP lines can occur if the following
requirements are met:
• Both nodes have DECnet licenses registered and loaded
• Both nodes have the asynchronous DDCMP driver NODRIVER loaded
• Both nodes have DYNSWITCH installed as a privileged shareable image
• The remote node has virtual terminals enabled
Managing Peripheral Devices 8–23