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C141-E226 3-15
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.
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 that has already been re-assigned.
Remark:
When a write protection is prohibited through the setting terminal, the auto alternate block
allocation processing specification is disabled.
IMPORTANT
Automatic alternate block allocation is made up to the following
quantities during the execution of one command:
ARRE = Twice
AWRE (Type 1) = Eight times
AWRE (Type 2) = Maximum number which can be processed
within the recovery time limit
If more than the above mentioned defective block is detected, the
alternate block assignment processing for the first defective block is
executed but the alternate block assignment processing for the
second one is not executed and the command being executed
terminates. However, the initiator can recover the twice error by
issuing the same command again.
When an error is detected in a data block in the data area, recovery
data is rewritten and verified in automatic alternate block allocation
during the execution of the READ or READ EXTENDED command.
Alternate block allocation will not be made for the data block if
recovery is successful.
Example: Even if the data error which is recoverable by the WRITE
LONG command is simulated, automatic alternate block
allocation will not be made for the data block.