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3-14 C141-E201
• Automatic alternate block allocation at write operation
If AWRE flag in the MODE SELECT parameter permits the automatic alternate block allocation,
the IDD executes two kinds of automatic alternate processing during WRITE command processing
as described below:
Type 1 (Reassignment of Uncorrectable Read Error)
1) Commands to be applied
- WRITE
- WRITE EXTEND
- WRITE at executing WRITE AND VERIFY
2) Application requirements
When any of the above commands is issued to LBA registered in the uncorrectable error log of
the READ command (LBA log of uncorrectable error while the READ command is executed),
the AWRE processing is applied.
3) AWRE processing
The following processings are performed when the LBA matches the one in the uncorrectable
error log:
a) Primary media check
- Creates an uncorrectable error pattern (invalid LBA pattern) in the position of the
error LBA, repeats the primary media check up to three times. If the error still occurs
after the check repeated three times, it is judged to be defective. Then, it performs the
alternate processing.
b) Alternate processing
- Alternate media check
Writes the data that causes an unrecoverable error into the alternate block, and
performs the media check.
(If the alternate block is a defective sector, the block is registered to the G list, another
alternate block is allocated.)
c) SA and defect map update processing (on alternate side)
When an error occurs in the alternate processing, this WRITE command terminates with error.
When the alternate processing normally terminates, the WRITE command is executed.
Depending on the alternate processing result, one of the following additional sense codes is
returned:
Alternate processing is succeeded: 01-OC-01
Type 2 (Reassignment of write fail sector)
1) Commands to be applied
- WRITE command
- WRITE EXTENDED command
- FORMAT UNIT
2) Application requirements / processing
When 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.