Using mass storage expanders, you can fill multiple DSSI buses: buses 0,1,2,3
supplied by the CPU, and a fourth and fifth DSSI bus using the KFQSA adapter.
Each bus can have up to seven DSSI mass storage devices (bus nodes 0–6). When
more than one bus is being used, and your system is using a nonzero allocation
class, you need to assign new unit numbers for storage devices on all but one of
the DSSI buses, as the unit numbers for all DSSI storage devices connected to a
system’s associated DSSI buses must be unique.
The following table illustrates the need to program unit numbers for a system
using more than one DSSI bus and a nonzero allocation class. In the case of the
nonzero allocation class, the operating system sees three of the ISEs as having
duplicate device names, which is an error, as all unit numbers must be unique.
Allocation Class=0
Nonzero Allocation Class
(Example: ALLCLASS=1)
R7CZZC$DIA1
$1$DIA1
$1$DIA2
$1$DIA3
$1$DIA0
$1$DIA1
$1$DIA2
$1$DIA3
$1$DIA4
$1$DIA5
$1$DIA6
R7ALUC$DIA2
R7EB3C$DIA3
R7IDFC$DIA0
R7IBZC$DIA1
R7IKJC$DIA2
R7ID3C$DIA3
R7XA4C$DIA4
R7QIYC$DIA5
R7DA4C$DIA6
Nonzero allocation class examples with an asterisk indicate duplicate device names.
For one of the DSSI busses, the unit numbers need to be reprogrammed to avoid this error.
*
Duplicate 1
*
Duplicate 2
*
Duplicate 3
*
TFDR1$MIA5
$1$MIA5
MLO-007176
R7BUCC$DIA0
$1$DIA0
Duplicate 0
*
Note
You should configure your system to have unique unit numbers even if
you have a standalone system using an allocation class of zero. That
C–4 Programming Parameters for DSSI Devices
