HP LTO 4 SCSI, LTO 4 FC, LTO 4 SAS manual Action, Console Message

Code	Sense Key	Interpretation
4h	HW ERROR	This indicates that the current I/O operation has failed due to a
		hardware failure.The FRU code in the sense data should indicate
		which part of the hardware is bad. The drive should not be used
		again until corrective action has been taken. Specific recovery
		depends on the operating system and application.
		For additional sense codes, see “4h—HW ERROR” on page 67.
	Action:	Whatever the additional sense code, the software should log the
		error, terminate the I/O, and report the appropriate error to the
		calling application. Whether the drive requires any further
		corrective action before it can be used again (such as a reset or
		manual intervention) depends on the additional sense code.
	Console Message:	Tape drive hardware failure
5h	ILLEGAL REQUEST	The last command sent to the drive, or the data sent because of the
		command, could not be accepted by the drive because it violated
		conditions imposed by the drive.
		For additional sense codes, see “5h—ILLEGAL REQUEST” on
		page 68. Also see the Illegal Command, Illegal Field, Fixed Bit,
		Reservation and Parameter List pre-execution checks.
	Action:	The software can retry the I/O, or else it can terminate the I/O and
		report an error to the calling application, particularly if the I/O has
		been retried a number of times and continues to fail with the same
		sense key. The specific retry or recovery strategy depends on the
		operating system.
	Console Message:	Illegal SCSI command requested
6h	UNIT ATTENTION	The operating conditions of the drive have been changed in some
		manner that the host should be aware of. For example, the drive
		may have gone online or been reset, the Mode parameters may
		have been changed, a second host may have changed the drive’s
		operating conditions, and so on.
		For additional sense codes, see “6h—UNIT ATTENTION” on
		page 69. Also see the Unit Attention pre-execution check.
	Action:	Recovery depends on the device class and the additional sense
		code. In general, the software should assume that mode settings
		and so on have been lost, and so should re-initialize the drive. The
		failed command will not have been executed and should be
		repeated.
		Note that for parallel SCSI, the host driver may need to renegotiate
		transfer parameters (for example, by using a PPR message) before
		continuing.
	Console Message:	Tape drive operating conditions may have
		changed

HP LTO Ultrium 4 drives technical reference manual, volume 2: software integration 55 HP restricted