Technical data

Managing Peripheral Devices
8.1 Understanding Device Names
• All local DSA tape devices are named MUAn, where n is a unique tape unit
number.
Use of a single controller letter requires that the unit number for each local DSA
device be unique. Duplicate unit numbers are possible if the local disks reside on
different controllers.
If the system is part of an OpenVMS Cluster environment, device names are
formatted in one of the following ways:
• If the device is attached to a single computer or hierarchical storage
controller (HSC) subsystem, the device name includes the node name in the
format node$ddcu, where node refers to the node name of the system that the
device resides on.
• If the device is to be accessed (or dual-ported) by two computers or HSC
subsystems, you must identify the device with a unique, path-independent
name that includes an allocation class.
The allocation class is a numeric value from 1 to 255, which is used to create
a device name in the form $allocation-class$device-name. For example, the
allocation class device name $11$DUA8 identifies a disk that is accessed by
two computers or HSC subsystems, both having an allocation class of 11.
• If the device is connected to a SCSI bus and the system parameter DEVICE_
NAMING is set to 1, you can assign the device a port allocation class, a
number from 0 to 32767 inclusive.
• If the device is assigned port allocation class 0, its name will be in the form
node $ddcuuu. The device cannot be located on a SCSI bus that is also
attached to another CPU.
• If the device is assigned a nonzero port allocation class, its name will be in
the form $allocation-class$ddAuuu. The device can be located on a SCSI bus
attached to another CPU, provided the other CPU has assigned the same port
allocation class to the SCSI bus.
For more information about the device name format in VAXcluster or OpenVMS
Cluster environments, refer to OpenVMS Cluster Systems.
For information about the naming conventions for Fibre Channel disk and tape
devices, see Guidelines for OpenVMS Cluster Configurations.
8.2 Getting Information About Devices on the System
Use the DCL command SHOW DEVICES to retrieve information about devices
on your system.
When you invoke the SHOW DEVICES command and do not specify a device or
use a qualifier, the system displays information about all recognized devices.
Note
If a device does not appear in the display, it is not recognized by the
system. The device may not be connected, or the driver may not be
loaded. For certain devices, you must manually connect them and load
their device drivers. For more information, see Section 8.4.
8–2 Managing Peripheral Devices