Hp C737990900 User Manual download pdf (Page 134)

134 Commands

■ The operation was abandoned without status (that is, a bus release

occurred) after what the drive perceived was a catastrophic error or when

an error occurred following the drive’s honoring of an

ABORT message.

Following the bus release, the drive performed “cleanup” activity that

failed. The Deferred Error refers to the reason for this failure.

When any one of the above occurs, the sense generated will be

DEFERRED

ERROR

sense. This sense persists until the host sends a command that has Unit

Attention as part of its pre-execution checks. When the Deferred Error pre-

execution check fails, the

DEFERRED ERROR sense is moved to the Current sense

and

CHECK CONDITION status is reported to the host. The host is then expected

to issue a

REQUEST SENSE command to recover the new Current sense data,

otherwise the data will be lost.

Write-Behind Deferred Errors:

If the Buffered Mode field of the MODE SELECT parameter header is not zero,

data buffering is enabled. If an error occurs in flushing the write-behind data,

DEFERRED ERROR sense is set for all hosts that the drive thinks have write-

behind data in the buffer. For each of these hosts, the following occurs when its

next command is to be executed:

■ If the command is WRITE or WRITE FILEMARKS the DEFERRED ERROR sense is

copied to Current sense and the error is changed to a Current error (the

Error Code field is set to 70h). The information bytes will contain residue

information reflecting the size of the write-behind queue plus the transfer

size of the current command.

CHECK CONDITION is reported. When the

host reads sense data with a

REQUEST SENSE, it will see an error for the

WRITE with residue information indicating data lost for that write and

previous writes.

■ If the command is not a write command and the Deferred Error check is

performed as part of the pre-execution checks,

CHECK CONDITION status is

reported. The

DEFERRED ERROR sense is copied to Current sense. The

DEFERRED ERROR sense is cleared. The host is expected to retrieve the sense

by sending a

REQUEST SENSE, otherwise the data will be lost.

Bus Release Deferred Errors:

The drive will release the bus to terminate an operation (such as READ) when

the host sends an

ABORT message or when the drive fails to send status due to

a catastrophic error.

In each case, the operation does not terminate immediately since the logical

position will have to be established on the other side of the block that was

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