Configuring and Managing Host-Based X.25 Links - Edition 6 (36939-90057)

Introduction
Host-Based Network Connections
Chapter 1
17
Nailed and Non-Nailed Connections
A nailed device is one that is permanently associated with an ldev number through the
NMMGR configuration of an MPE/iX system. Any time a connection exists between a
system and one of its nailed devices the same ldev number will belong to that device.
This ldev number is reserved for the use of that connection and only that connection.
Serial devices attached locally or though a modem and PAD devices attached through a
private or public PAD may be configured as either nailed or non-nailed ldevs. Serial
devices that will be accessed programmatically at any time must be configured as nailed
ldevs. Since printers are accessed programmatically, ALL printers must be configured as
nailed devices.
A non-nailed device is a device that is able to establish a connection to an MPE/iX host
system but has no permanently assigned ldev number in the NMMGR configuration file
of that system. Instead, ldev numbers are dynamically associated with a device
connection at the time the user requests the connection. The user of a non-nailed device
is able to establish a session provided two conditions are met: a connection must be
available on the host and the non-nailed device profile specified in the host configuration
must match the characteristics of the device requesting the connection.
When the user at a locally or PAD-connected device with a non-nailed connection logs on
to the system, an ldev number is assigned from a pool of available ldev numbers defined
through the host system’s NMMGR configuration. When the connection is ended (the
user logs off) the assigned ldev number is returned to the pool of ldev numbers and
becomes available for use by a different device connection.
Non-nailed device connections provide several major advantages. They simplify the
configuration that must be done on each MPE/iX system, since configuration values do
not have to be entered separately for each PAD device that will be able to access that
system. Non-nailed connections also make it possible for you to add serial devices to the
network without having to reconfigure each host so that it will recognize the additional
devices. Finally, configuring a pool of non-nailed devices makes it possible for the
number of users with potential access to a system to exceed the session limit of the
system. The pool of non-nailed ports that you configure cannot exceed the session limit,
and the number of users logged on at a given time must still be within the session limit.
When the user connects to the system through a public PAD, the connection will use a
non-nailed device on the host.
Managed and Non-Managed DTCs
When a DTC is configured in a Host-Based environment the DTC is managed by the
management platform that downloads the DTC configuration and performs all the other
management functions such as DTC resets, uploads and controls the operation of all
DTC functions. It is possible to configure the same DTC on another HP e3000 system so
that it is a non-managed DTC on the system where the configuration is entered. A DTC
would be configured as a non-managed DTC on a system in order to configure nailed
devices that can be accessed from a shared DTC. In this way a terminal, printer or PAD
device can be shared as a nailed device on multiple systems. This sharing of serial
devices uses the Host-Based Switching features of the DTS subsystem.
The DTC is managed by the management platform that has the proper DTC LAN
Station Address defined. To configure the same DTC as a non-managed DTC on another
HP e3000, you create a DTC configuration with the same DTC Node Name and configure
the DTC LAN station address as 00-00-00-00-00-00.