How MPE/iX Identifies Devices

A non-nailed device is able to establish a connection to the HP 3000 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.

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 is always connected through the access port on the HP 3000 Series 900 computer. The system console's ldev number is assigned during system initialization and remains constant unless it is modified through the SYSGEN utility and the host is restarted.

Printers are assigned ldev numbers during configuration making them nailed devices. Each printer keeps the same ldev number unless that number is modified through NMMGR and the host is restarted.

Usually, many terminals are connected to a DTC. Some terminals can have permanent ldev numbers assigned during NMMGR configuration.

Other terminals might not have permanent ldev 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" 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.

Sometimes plotters are connected to a DTC. Plotters, like printers, always have assigned ldev numbers (always a nailed device).

HP PowerTrust UPSs can be connected to DTCs as nailed devices. Only the MPE/iX operating system accesses these 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 devices.