Configuring and Managing Host-Based X.25 Links - Edition 5 (36939-90054)

Chapter 1 19
Introduction
Host-Based X.25 Configuration Concepts
NOTE The X.25 iX System Access procedure described in this manual assumes
the use of guided configuration. While it is possible to configure this
link using non-guided configuration, Hewlett-Packard strongly
recommends the use of the guided configuration process.
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. While
devices attached through a private or public PAD may be either nailed
or non-nailed, all serial devices attached either locally or through a
modem must be configured with nailed connections on host-based
systems.
Since only nailed devices can be accessed programmatically, all printers
must also be nailed, as must any other serial devices that will be
accessed programmatically at any time.
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 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.