Quantum DLTtape DLT1, Interface Manual

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Chapter 4: SCSI Commands
4-96 July 2004 81-81276-01 Rev A01
4.18 REQUEST SENSE (03h)
The REQUEST SENSE command tells the target to transfer sense data to the initiator.
Figure 4-68. REQUEST SENSE (03h) Command Descriptor Block — Data Format
The Sense Data is valid for a CHECK CONDITION or RESERVATION CONFLICT status returned
on the previous command. The target preserves the Sense Data bytes until they are retrieved by the
REQUEST SENSE command or until receipt of any other command from the same initiator.
If the tape drive receives an unsolicited REQUEST SENSE, it returns Sense Data with the appropriate
values in the EOM, Sense Key, Additional Sense Code, and Additional Sense Code Qualifier. The
positional information provided reflects the logical position of the tape drive. The tape drive returns
Table 4-57.
RELEASE UNIT (17h) Command Descriptor Block — Field Descriptions
Field Name Description
LUN Logical Unit Number. The target ignores this field. Only an IDENTIFY message
can change the LUN.
3rdPty The third-party release option for RELEASE UNIT allows an initiator to release a
logical unit that was previously reserved using the third-party reservation option.
If the third-party (3rdPty) bit is 0, the third-party release option is not requested. If
the 3rdPty bit is 1, the tape drive is released if it was originally reserved by the
same initiator using the third-party reservation option and if the tape drive is the
same SCSI device that was specified in the Third-party Device ID field.
Medium Changer
Considerations The optional Element Reservation feature defined for Medium Changer devices in
SCSI-2 is not supported. The RELEASE command is defined the same as for the
tape drive. The entire loader can be released. RESERVE/RELEASE of the Loader
and Drive LUNs are handled independently.
Bit
Byte
7 6 5 4 3 2 1 0
0 Operation Code (03h)
1 Logical Unit Number Reserved
2 - 3 Reserved
4 Allocation Length
5 Unused Reserved Flag Link