Request Sense (03h)

The Request Sense command (03) requests the library transfer sense data to the initiator.

Logical libraries use an FC-2 conforming transport that provides autosense. This means that sense data for a failed command is always returned with a Check Condition status in the command response and is never saved by the target. Therefore, Request Sense will always return Sense Data with a Sense Key set to No Sense and ASC/ASCQ fields set to 0.

However, all Sense Keys and associated ASC/ASCQ fields that can be returned by other commands are documented here.

Figure 3-29 Descriptor Block - Request Sense (03h)

Description of "Figure 3-29 Descriptor Block - Request Sense (03h)"

Desc

The Desc bit indicates which sense data format shall be returned.

The library returns a value of 0, indicating fixed format sense data is returned.

Allocation Length

This field specifies the number of bytes that the initiator has allocated for returned sense data. The library provides a maximum of 14h (20d) bytes of sense data.

Request Sense Data Definitions

Figure 3-30 Descriptor Block - Request Sense Data Definitions

Description of "Figure 3-30 Descriptor Block - Request Sense Data Definitions"

Valid

0 = The library does not return data in the Information field.

Error Code

70h = The library returns only current errors.

Segment Number

00h = The library does not support segment numbers.

Sense Key

Describes the error, along with ASC and ASCQ. See Additional Sense Codes and Qualifiers.

0h = No Sense, indicating a successful command.

2h = Not Ready

3h = Medium Error

4h = Hardware Error

5h = Illegal Request

6h = Unit Attention

Bh = Aborted Command

Information

00h = The library does not support this field.

Additional Sense Length

0Ch = Indicates there are 12d bytes of additional sense bytes to follow. This value is not truncated to reflect the actual transfer length.

Command Specific Information

00h = The library does not support this field.

Additional Sense Code (ASC)

Describes the error. See Additional Sense Codes and Qualifiers.

Additional Sense Code Qualifier (ASCQ)

Describes the error. See Additional Sense Codes and Qualifiers.

Field Replaceable Unit Code

00h = The library does not support this field.

SKSV (Sense Key Specific Valid)

1 = The C/D and field pointer are valid

0 = Ignore the C/D and field pointer

C/D (Command/Data)

0 = The check condition status resulted from illegal parameter in the parameter list.

1 = The check condition status resulted from illegal parameter in the CDB.

BPV (Bit Pointer Valid)

0 = The library does not support this field.

Bit Pointer

0h = The library does not support this field.

Field Pointer

The number of the byte where the error occurred. When a multiple-byte field is in error, the Field Pointer contains the value of the most significant byte of the field, which is lowest byte number. Byte numbers start at 00.

Additional Sense Codes and Qualifiers

Not Ready Sense Key Code (2h)

The library generates a Not Ready error code if you send a command when the library is in a not ready state.

Description	Sense Key	ASC	ASCQ
Not Ready, Maintenance Mode	2h	04h	81h

Not Ready, Maintenance Mode: The library was placed in maintenance mode from the operator panel or user interface. The logical library is offline.

Hardware Error Sense Key Code (4h)

The library generates a Hardware Error if it detects a hardware or firmware error during command execution.

Description	Sense Key	ASC	ASCQ
Hardware Error, Tape Drive	4h	40h	02h
Hardware Error, Internal Target Failure	4h	44h	00h

Hardware Error, Tape Drive: An operation to the drive failed. The problem could be the tape drive or the interface between the library and tape drive.
Hardware Error, Internal Target Failure: The library generates a hardware error when an unexpected condition is detected by ACSLS software that controls the SCSI interface. This error is used for arbitrary limitations of the software.

Illegal Request Sense Key Code (5h)

Any illegal parameters in the CDB or parameter list for a particular command generates an Illegal Request sense key.

In some cases, additional information is available in Byte 15 of the sense data, which includes the sense-key-specific-value (SKSV) and command/data (C/D) fields. This information indicates the byte in the command descriptor block or the parameter list that is in error. If available, the SKSV bit in the sense data is set to 1.

Description	Sense Key	ASC	ASCQ	SKSV
Invalid Command Operation Code	5h	20h	00h	Yes
Invalid Element Address	5h	21h	01h	No
Invalid Field in CDB	5h	24h	00h	Yes
Logical Unit Not Supported	5h	25h	00h	No
Incompatible Medium	5h	30h	00h	No
Saving Parameters Not Supported	5h	39h	00h	Yes
Medium Not Present, Drive Not Unloaded	5h	3Ah	00h	No
Destination Element Full	5h	3Bh	0Dh	No
Source Element Empty	5h	3Bh	0Eh	No

Unit Attention Sense Key Code (06h)

The library generates a Unit Attention sense key for all initiators if the library needs to inform the host of an asynchronous event.

Description	Sense Key	ASC	ASCQ
Not Ready-to-Ready Transition	06h	28h	00h
CAP Element Accessed	06h	28h	01h
Mode Parameters Changed	06h	2Ah	01h
Reservations Preempted	06h	2Ah	03h
Reservations Released	06h	2Ah	04h
Registrations Preempted	06h	2Ah	05h
LUNs Data Has Changed	06h	3Fh	0Eh

Not Ready to Ready Transition: The library transitioned to a Ready state from a Not Ready state. The library sends this unit attention to all initiators.
CAP Element Accessed: The operator opened and closed the CAP. The library sends this unit attention to all initiators. You can issue a Read Element Status command to obtain an updated inventory (see Read Element Status (B8h).
Mode Parameters Changed: The operator added or removed elements from a partition. Send a Read Element Status (B8h) command to obtain an updated inventory. Send a Mode Sense command with Element Address page code to request the current count of each element type.
Persistent Reservations/Registrations Preempted or Released: A different initiator issued a Persistent Reservation Out command that cleared the registration for this initiator or cleared a reservation that affects this initiator.
LUNs Data Has Changed: The LUN configuration for the initiator has changed. The library sends this unit attention when the operator adds or removes a LUN connection from a partition for the initiator.

Aborted Command Sense Key Code (0Bh)

The library generates an Aborted Command error code when a SCSI command is aborted.

Description	Sense Key	ASC	ASCQ
Command Overlap	0Bh	4Eh	00h

Command Overlap: The library detected another command from an initiator while one was already in process.