DEC VAX 4000 300 Manual page 97

NOTE: Each of the above parameters, with the exception of the Bus Node
ID, are programmed and examined using the console-based Diagnostic
and Utility Program (DUP) driver utility. The Bus Node ID is physically
determined by the numbered bus node ID plug that inserts into the device's
front panel.
A brief description of each parameter follows:
The Bus Node ID parameter is provided by the bus node ID plug on the
device's front panel. Each DSSI bus can support up to eight nodes, 0–7.
Each DSSI adapter and each device count as a node. Hence, a DSSI bus
can support up to seven devices, bus nodes 0–6 (with node 7 reserved for
the storage adapter); in a dual-host configuration up to six devices, 0–5
(with nodes 6 and 7 reserved for the storage adapters). Refer to Chapter 3
for instructions on changing bus node ID plugs.
The ALLCLASS parameter determines the device allocation class. The
allocation class is a numeric value from 0 to 255 that is used by the VMS
operating system to derive a path-independent name for multiple access
paths to the same device. The ALLCLASS firmware parameter corresponds
to the VMS SYSGEN parameter ALLOCLASS.
DSSI devices are shipped from the factory with a default allocation class of
zero. Each device to be served to a cluster should have a nonzero allocation
class that matches the allocation class of the system. Refer to the VMS
VAXcluster manual for rules for specifying allocation class values.
The UNITNUM parameter determines the unit number of the device. By
default, the device unit number is supplied by the bus node ID plug on
the device's front panel. Systems with multiple DSSI busses, as described
later in this section, require that the default values be replaced with unique
unit numbers. To set unit numbers and override the default values, you
use the console-based DUP driver utility to supply values to the UNITNUM
parameter and to set a value of zero to device parameter FORCEUNI.
The FORCEUNI parameter controls the use of UNITNUM to override the
default device unit number supplied by the bus node ID plug. When
FORCEUNI is set to a value of zero, the operating system uses the value
assigned to the UNITNUM parameter; when FORCEUNI is set to a value
of one, the operating system uses the value supplied by the bus node ID
plug.
The NODENAME parameter allows each device to have an alphanumeric
node name of up to eight characters. DSSI devices are shipped from the
factory with a unique identifier, such as R7CZZC, R7ALUC, and so on. You
can provide your own node name.
B–2 VAX 4000 Model 300 Operation