The missing device file /dev/dsk/c0d0s3, for example, can be created by the
"mknod" command:
mknod /dev/dsk/c0d0s3 b 24 3
chmod 600 /dev/dsk/c0d0s3
chown bin /dev/dsk/c0d0s3
chgrp bin /dev/dsk/c0d0s3
Note that 24 is the major device number, 3 is the minor device number for
/dev/dsk/c0d0s3, and b indicates a block device type. Of course, you have
to be "root" to do it.
The "pname" command seems to do the same thing. It will automatically
create the file in the /dev/dsk directory, if c0d0s3 doesn't exist. In your
case, for example, pname -c0 -s3 "Unreserved 1".