Sun Oracle Storage Tek T10000, Справочное руководство

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FCP Information Units
50 T10000: Interface Reference Manual • January 2011 • E20425-01
Because the first word of FCP_RSP frames are reserved in FCP, these bits
are set to zero, regardless of the content of the SCSI Status portion of the
payload. SCSI Initiators do not rely on word 0, bits 31 and 30 in FCP_RSP to
determine success or completion status of a command. An FCP_RSP
following a data-in sequence (I3) may or may not be treated as a streamed
sequence.
Residual Checking
Residual checking falls under the following categories:
• SCSI Targets that transfer exactly FCP_DL data bytes during the
FCP_DATA IUs set the FCP_RESID_UNDER to a value of ‘0’b.
When FCP_RESID_UNDER is set to ‘0’b, the SCSI Initiator tries to
determine if all of the expected data was transferred by comparing the
FCP_DL to the actual number of bytes transferred. If these values are not
the same, the ULP is notified so that the appropriate action can be taken.
• SCSI Targets that transfer less than FCP_DL data bytes during the
FCP_DATA IUs set the FCP_RESID_UNDER to a value of ‘1’b.
If the FCP_RESID_UNDER bit is set to ‘1’b, a transfer that did not fill the
buffer to the expected displacement. Failure to transfer FCP_DL bytes
does not necessarily indicate an error for some devices and commands.
• If the FCP_RESID_OVER bit is set, the transfer was truncated because
the data transfer required by the SCSI command extended beyond the
displacement value of FCP_DL. Those bytes that could be transferred
without violating the FCP_DL value may or may not have been transferred.
• Commands that do not contain an FCP_DATA IUs, FCP_RESID_UNDER
and FCP_RESID_OVER are set to ‘0’b, and the value of the FCP_RESID
is undefined.