User's Manual

Table 5-1 Problems Detected By Domain Validation (continued)
Possible CauseProblem
Poor shielding or grounding.Excessive cross talk
Poor shielding or grounding.Excessive system noise
When Domain Validation determines that communication with the target device is not possible
at the maximum data transfer rate supported by the adapter (Ultra320), it writes a warning
message to the /var/adm/syslog.log file. Example 5-2 shows a typical log entry:
Example 5-2 Typical Domain Validation syslog Entry
SCSI Ultra320 0/3/1/1 instance 9:
Domain Validation forced SCSI Parameter fallback.
Target ID 2 - Currently operating at Ultra160 Wide.
The data transfer rate then “falls back” by one level to a slower setting. Table 5-2 lists the fallback
levels for most systems:
Table 5-2 Domain Validation Fallback Levels
Data Transfer Rate (MB/s)Bus WidthSCSI Rate
320WideUltra320
160WideUltra160
80WideUltra2 Wide
40NarrowUltra2
40WideUltra Wide
20NarrowUltra
20WideFast Wide
10NarrowFast
<5NarrowAsynchronous
NOTE: The number of entries in Table 5-2 is subject to change. It is provided here to give you
an example of how the fallback procedure works.
Domain Validation tests are run on all targets on the SCSI bus, even those targets that do not
have Ultra320 capabilities. The starting point in Table 5-2 depends on the parameters that were
negotiated for any particular target. Since a SCSI bus can contain up to 15 targets, several different
SCSI parameters may be in effect at any one time on the bus, because Domain Validation is
running on all of the targets at the same time.
For example, if the parameters originally negotiated during the normal SCSI initiator/target
communications are equivalent to Ultra320, but Domain Validation determines that the SCSI
bus or the target cannot support that data transfer rate, then Domain Validation falls back to
Ultra160. After the fallback, Domain Validation repeats its test. If the bus or target still cannot
support the transfer rate, Domain Validation falls back another level, to Ultra2 Wide; then to
Ultra2 Narrow, and so forth. As long as failures occur, fallback continues, one level at a time,
until the lowest level in Table 5-2 (Asynchronous) is reached. Note that Domain Validation does
not generate a fallback warning message such as Example 5-2 (page 54) each time that it falls
back a level, but only when it successfully settles at a level. If a failure occurs at the lowest level,
the device is taken offline and a Domain Validation failure message is written to the
/var/adm/syslog.log file. For example:
54 Troubleshooting