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2. When errors in the data area are recovered from by ECC correction
processing, before implementing alternate block allocation processing,
rewriting of the recovered data and a verify check (rereading) are performed.
If data are recovered by rewriting, alternate block allocation of that data
block is not performed.
(2) Auto alternate block allocation processing during a write operation 1
This function is enabled by specifying "1" in the AWRE flag in the MODE
SELECT parameters. Furthermore, this function is applicable to the following
commands only.
•
WRITE command
•
WRITE EXTENDED command
•
WRITE AND VERIFY command
The function handles the unrecoverable media error (MEDIUM ERROR
[= 3]/Read Retries Exhausted [= 11 - 01]) detected when the number of read
retries for an error reaches the specified value in the "Number of retries during
READ" field of the MODE SELECT parameter (refer to Section 5.3.1 (3)). In
such cases, if this function is enabled, the IDD registers the data block as the
target block of AWRE processing. If the WRITE, WRITE EXTENDED, or
WRITE AND VERIFY command is executed for the same data block, an
alternate block is allocated to the data block. The data field of the alternate block
is verified, and the required write data is written in the data field. This alternate
block allocation is applied with the same processing as that of the REASSIGN
BLOCKS command.
If multiple data blocks are the target blocks of AWRE processing when a single
command is executed, this function applies to all of these data blocks. If an
unrecoverable media error (MEDIUM ERROR [= 3]/Read Retries Exhausted [=
11 - 01]) is then detected during the read operation for a data block, INIT should
issue the WRITE, WRITE EXTENDED, or WRITE AND VERIFY command to
the data block. Thus, auto alternate block allocation is applied, and error recovery
is possible.
Remark 1:
Remark 2:
If error recovery is completed by rewriting the data to the data block, alternate
block allocation is not performed for this data block. The data block is removed
as the target of AWRE processing.
C141-C009
When this function has been set (AWRE = "1"), up to eight
unrecoverable media errors (MEDIUM ERROR [= 3]/Read Retries
Exhausted [= 11 - 01]) detected during the read operation of the
READ or READ EXTENDED command can be recorded. This
recorded information is cleared when power is turned off or
microcode is downloaded with the WRITE BUFFER command
(regardless of whether save is specified).
Before data for a data block is allocated to an alternate block in
AWRE processing, the data is written again to the data block and
verified (re-read).
5.3 Disk Drive Error Recovery Processing
5-27
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