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C141-E167 5 - 1
CHAPTER 5 Sense Data Error Recovery Methods
5.1 Sense Data
5.2 INIT Error Recovery Methods (Recommended)
5.3 Disk Drive Error Recovery Processing
In this chapter, the configuration and contents of sense data reported to the INIT (initiator) when an error
occurs, etc., key information for interpreting error states, recommended procedures for error recovery
processing that should be executed by software in the INIT and error recovery processing executed internally
by the IDD are described. Furthermore, see Chapter 3, “SCSI Bus Error Recovery Processing” in the “SCSI
Physical Interface Specifications” concerning recovery processing for errors detected in operations on the
SCSI bus.
5.1 Sense Data
When the IDD reports a CHECK CONDITION status, or in cases when some fatal error is detected in
connection with the SCSI bus, and as a result, the command that is currently being executed, or the
commands in the stack are cleared, it generates sense data for the INIT that issued that command. The
INIT can fetch the sense data by issuing a REQUEST SENSE command.
5.1.1 Sense data format
The IDD’s sense data is in the so-called “Expanded Sense Data” format. The expanded sense data
format supported by the IDD is shown in Figure 5.1.
Notes:
1. In the SCSI specifications, each device is permitted to define whatever it chooses after byte
18 of the expanded sense data, and the length and format differ for each device. The length
of expanded sense data is displayed in the sense data, so by analyzing the sense data which
it receives, the INIT can know its effective length.
2. In the REQUEST SENSE command, even if a Transfer byte length that is shorter than the
length of the sense data supported by the device which is the object of the command, the
command will terminate normally, but in that case, some of the sense data only will be
received and the remaining information will be lost. Sufficient caution should be exercised
with regard to the devices connected to the INIT and all the sense data of those devices
should be read.