HP 3000 Manuals HP 3000 Manuals
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 3000 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 3000 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 3000 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 3000
computer has no permanently assigned 1dev 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 3000 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.
NOTE If two or more systems have access to the same nailed device,
contention for that device might exist. Only one system can access
a nailed device at any time. For example, if system A accesses the
nailed device, system B will not be able to access the nailed
device at the same time. The nailed device is being used by system
A and is probably not broken, even though it can't be reached.
An ldev number can be assigned to any asynchronous device, including the
following:
* The system console.
* Printers,
Terminals,and Plotters.
* Other serial devices.
System Console.
The system console is always connected through the access port on the HP
3000 Series 900 computer. The system console's 1dev number is assigned
during system initialization and remains constant unless it is modified
through the SYSGEN utility and the host is restarted.
Printer.
Printers are assigned ldev numbers during configuration making them
nailed devices. Each printer keeps the same 1dev number unless that
number is modified through NMMGR and the host is restarted.
Terminals.
Usually, many terminals are connected to a DTC. Some terminals have
permanent 1dev numbers assigned during NMMGR configuration.
Other terminals might not have permanent 1dev numbers assigned
(non-nailed). Instead, these terminals will use an ldev number from a
pool of available ldev numbers. Non-nailed devices can be configured if
PC-based network management is used. Refer to "Nailed Devices" and
"Non-Nailed Devices" used earlier in this chapter for more information.
Terminal users should know the physical device address for their
terminal. If a terminal is having problems, the physical device address
is needed to troubleshoot the terminal. The physical device address
consists of identifiers for the DTC, the interface card, and the port to
which the device is connected. Refer to "Device Physical Path" later in
this chapter for more information.
Plotters.
Sometimes plotters are connected to a DTC. Plotters, like printers,
always have assigned ldev numbers (always a nailed device).
UPSs.
HP PowerTrust UPSs can be connected to DTCs as nailed devices. Only the
MPE/iX operating system accesses these devices.
Other Non-Supported Devices.
Devices that conform to Hewlett-Packard's asynchronous protocol and are
capable of being physically connected to the DTC can be controlled
through Asynchronous Serial Communications (ASC). This includes test
instruments, data collection devices, etc. To determine if a device can
be non-nailed or if it must be nailed, refer to "Nailed Device" and
"Non-Nailed Device" in this chapter. Contact your Hewlett-Packard
support representative for more information on non-supported devices.
Take extreme care when connecting non-supported devicesn-.
Device Physical Path
Each asynchronous device (excluding the system console, PADs, and
Telnet/iX devices) is connected to a port on an interface card within a
DTC; this is the device's physical path. The address for the physical
path, or the physical device address, consists of identifiers for the
DTC, the interface card, and the port to which the device is connected.
Note that the physical device address can be used to troubleshoot a
device and its connection.