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

Describing Asynchronous Devices
How MPE/iX Identifies Devices
Chapter 9
156
How MPE/iX Identifies Devices
Asynchronous devices (terminals, printers, plotters, etc.) are located and communicated
with in two ways:
• Through the device’s logical device (ldev) number.
• Through the physical path from the HP e3000 to the asynchronous device.
Logical Device Numbers
The ldev number is a value that the MPE/iX operating system uses to recognize attached
devices. Terminals attached to Datacommunications and Terminal Controllers (DTCs),
managed by an HP e3000 host, are configured with nailed ldev numbers. Terminals
attached to DTCs, managed by an OpenView Windows Workstation, can be configured to
have either nailed ldev numbers or non-nailed ldev numbers on the host systems to
which they have access. Logical device numbers are associated with nailed devices
during configuration.
A nailed device has a permanently assigned ldev number. A non-nailed device has an
ldev number associated with it after a session is requested.
A terminal connected through a DTC to multiple HP e3000 computers can have nailed
connections on more than one host system. Alternatively, a terminal can have a nailed
connection on one host system and a non-nailed connection on another, or it can be
configured to have non-nailed connections on all of the systems to which it has access.
Non-Nailed Devices
A non-nailed device is able to establish a connection to the HP e3000 computer but has
no permanently assigned ldev number in the NMMGR configuration file. The user of a
terminal connected as a non-nailed device can establish a session provided a connection
is available and the host configuration specifies a device profile matching the
characteristics of the device requesting the connection.
When the user logs onto the host, an ldev number is assigned from a pool of available
ldev numbers. When the connection is ended (the user logs off), the ldev number is
returned to the pool of ldev numbers and becomes available for use by a different device.
It is possible to configure non-nailed devices only when PC-based management is used.
Nailed Devices
A nailed device is permanently assigned an ldev number through the NMMGR
configuration of the HP e3000 computer. Any time a connection exists between a
computer and one of its nailed devices, the same ldev number will belong to that device.
Only nailed devices can be accessed programmatically. All printers must be nailed, as
must any device that will be accessed programmatically. Devices with permanently
assigned ldev numbers keep the same ldev number unless that number is modified
through NMMGR and the host is restarted. All devices are nailed when host-based
network management is used.