C.1 DSSI Device Parameters
Six principal parameters are associated with each DSSI device:
• Bus Node ID
• ALLCLASS
• UNITNUM
• FORCEUNI
• NODENAME
• SYSTEMID
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.
Bus Node ID
This 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, in a single-
system configuration, a DSSI bus can support up to seven devices,
bus nodes 0–6 (with node 7 reserved for the adapter); in a two-system
DSSI VAXcluster configuration, up to six devices, 0–5 (with nodes 6
and 7 reserved for the adapters); in a three-system DSSI VAXcluster
configuration, up to five devices, 0–4 (with nodes 5, 6, and 7 reserved
for the adapters). Refer to Chapter 3 for instructions on changing bus
node ID plugs.
ALLCLASS
This 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.
C–2 Programming Parameters for DSSI Devices
