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This mode is used to manage and retrieve error history (see SPC-4).

If the device server is unable to process a READ BUFFER command with the MODE field set to 1Ch because of a vendor specific condition, then the device server shall terminate the READ BUFFER command with CHECK CONDITION status, with the sense key set to ILLEGAL REQUEST, and the additional sense code set to COM-MAND SEQUENCE ERROR.

The BUFFER ID field (see table 102) specifies the action that the device server shall perform, and the parame-ter data, if any, that the device server shall return.

The command shall be terminated with CHECK CONDITION status with the sense key set to ILLEGAL REQUEST and the additional sense code set to OPERATION IN PROGRESS if the device server receives a READ BUFFER command:

a) with the MODE field set to 1Ch;

b) with the BUFFERID field set to a value that table 102 shows as constrained by error history I_T nexus;

c) if an error history I_T nexus exists and the command is received from an I_T nexus that is different that I_T nexus; and

d) an error history snapshot exists.

BUFFER OFFSET field

The BUFFER OFFSET field specifies the byte offset from the start of the buffer specified by the BUFFER ID field from which the device server shall return data. The application client should conform to the offset boundary requirements indi-cated in the READ BUFFER descriptor (see 3.24.1.3). If the buffer offset is not one of those shown in table 102 or the device server is unable to accept the specified buffer offset, then the device server shall terminate the READ BUFFER Table 102. Error history BUFFER ID field

Code Description Buffer offset

Error history I_T nexus constrained

Reference

00h Return error history directory 0000h Yes 3.24.1.7.2

01h Return error history directory and create new error history snapshot (see 1.1and SPC-4)

0000h Yes 3.24.1.7.2

02h Return error history directory and establish new error history I_T nexus (see 1.1and SPC-4)

0000h No 3.24.1.7.2

03h Return error history directory, establish new error history I_T nexus, and create new error history snapshot

0000h No 3.24.1.7.2

04h to 0Fh Reserved Yes

10h to EFh Return error history 0000h to FFFFh Yes 3.24.1.7.3

F0h to FDh Reserved Yes

FEh Clear error history I_T nexus Ignored Yes 3.24.1.7.4

FFh Clear error history I_T nexus and release error history snapshot

Ignored Yes 3.24.1.7.5

3.24.1.7.2 Error history directory

Whenever allowed by established error history I_T nexus constraints (see 3.24.1.7.1), if any, all error history device server actions return an error history directory (see table 104). Some error history device server actions also discard the existing error history snapshot (see SPC-4) and create a new error history snapshot (see table 103).

field

Establish new error history I_T nexus (see SPC-4)

Error history snapshot (see SPC-4) Preserved (if exists) Created

00h No ^a Yes No ^b

01h No ^a No Yes

02h Yes Yes No ^b

03h Yes No Yes

a If no error history I_T nexus is established, a new one is established.

b If no error history snapshot exists, a new one is created.

Table 103 — Summary of error history directory device server actions

BUFFER ID

The error history directory is defined in table 104.

Table 104. Error history directory Bit

Byte

7 6 5 4 3 2 1 0

0 (MSB)

T10 VENDOR INDENTIFICATION

7 (LSB)

8 VERSION

9 Reserved

EHS_RETRIEVED EHS_SOURCE CLR_SUP

10

Reserved 29

30 (MSB)

(n-31)

31 (LSB)

Error history directory list

32 Error history directory entry [first]

(see table 107) 39

.. .

n-7 Error history directory entry [last]

(see table 107) n

T10 VENDOR INDENTIFICATION field

The T10 VENDOR INDENTIFICATION field contains eight bytes of left-aligned ASCII data identifying the manufacturer of the logical unit. The T10 vendor identification shall be one assigned by INCITS.

Note. The T10 VENDOR INDENTIFICATION field may contain a different value than the VENDOR INDENTIFICATION field in the standard INQUIRY data (see 3.6.2) (e.g., this field may indicate a disk drive component vendor while the standard INQUIRY data indicates the original equipment manufacturer).

VERSION field

The VERSION field indicates the version and format of the vendor specific error history. The VERSION field is assigned by the vendor indicated in the T10 VENDOR INDENTIFICATION field.

DIRECTORY LENGTH

EHS_RETRIEVED (error history retrieved) field

The error history retrieved (EHS_RETRIEVED) field (see table 105) indicates whether a clear error history device server action has been requested for the error history snapshot. EHS_RETRIEVED field shall be set to 00b or 10b when the error history snapshot is created.

Table 105. EHS_RETRIEVED field Code Description

00b No information

01b The error history I_T nexus has requested buffer ID FEh (i.e., clear error history I_T nexus) or buffer ID FFh (i.e., clear error history I_T nexus and release snapshot) for the current error history snapshot.

10b An error history I_T nexus has not requested buffer ID FEh (i.e., clear error history I_T nexus) or buffer ID FFh (i.e., clear error history I_T nexus and release snapshot) for the current error history snapshot.

11b Reserved

EHS_SOURCE (error history source) field

The error history source (EHS_SOURCE) field (see table 106) indicates the source of the error history snapshot.

Code Description

00b The error history snapshot was created by the device server and was not created due to processing a READ BUFFER command.

01b Error history snapshot was created due to processing of the current READ BUFFER command 10b Error history snapshot was created due to processing of a previous READ BUFFER command 11b Reserved

CLR_SUPC (clear support) bit

1 A clear support (CLR_SUP) bit set to one indicates that the CLR bit is supported in the WRITE BUFFER command download error history mode (see 3.70).

0 A CLR_SUP bit set to zero indicates that the CLR bit is not supported.

DIRECTORY LENGTH field

The DIRECTORY LENGTH field indicates the number of error history directory list bytes available to be transferred. This value shall not be altered even if the allocation length is not sufficient to transfer the entire error history directory list.

Table 106 — EHS_SOURCE field

The error history directory list contains an error history directory entry (see table 107) for each supported buffer ID in the range of 00h to EFh. The first entry shall be for buffer ID 00h and the entries shall be in order of ascending buffer IDs. The supported buffer IDs are not required to be contiguous. There shall not be any entries for buffer IDs greater than or equal to F0h.

Table 107. Error history directory entry Bit

The SUPPORTED BUFFER ID field indicates the error history buffer ID associated with this entry.