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Sense Data and Error Recovery Methods
386 C141-C013
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.
(3) Auto alternate block allocation processing during a write operation 2 (servo auto
alternate)
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
When this function is permitted, if, during WRITE/WRITE EXTENDED
command detects any Servo error (e.g. Write offtrack error) and cannot be
recovered within pre-determined retry number (specified in Mode Parameter).
For the sectors around defective Servo, alternate blocks are allocated and the data
of this WRITE commands are re-written.
Sectors to be made AWRE shall be following:
• the sector where the error occurs and the latter sectors and,
• the sectors whose data are logically continual and stored in Cache,
• the sectors which will be processed in this Write command and,
• the sectors which locate between erroneous Servo -1 and +1 (including Split
sector)
This function is also applied for the sector which has already been re-assigned.
6.3.3 Error recovery processing control
The INIT can, by specifying the MODE SELECT parameters, can control the
error recovery processing (retries) of the HDD with respect to each type of error
related to the disk drive.
Table 6.7 shows the types of error and the method of specifying the number of
retries for those errors. for those items where the INIT can specify the number of
retries, normally, it is recommended that the default value or a greater number of
times be specified. If a value smaller than the default value is specified, and
commands are terminated abnormally without error recovery processing
succeeding, the INIT should reset the corresponding MODE SELECT parameters
at the default value, then reexecute the original commands.
The MODE SELECT parameters related to disk drive error recovery processing
which the INIT can specify are shown below. See the description of the MODE
SELECT command (Section 4.1.4) concerning details of the functions of each
parameter. The INIT can issue the MODE SELECT or MODE SELECT