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If the error cannot be recovered from even when retry processing is executed the
specified number of times, the IDD terminates the command which is currently
being executed with a CHECK CONDITION status. The sense key in the sense
data at this time is "HARDWARE ERROR [=4]" and the ASC/ASCO indicates
"Mechanical positioning error [=15-01]" or "Positioning error detected by read of
medium [=15-02]."
(2) Read error in uncorrectable data
This error is a failure to detect the Sync Mark pattern during reading of data or an
ECC error for which correction processing is impossible. If this error is detected,
the IDD, after waiting one revolution of the disk media, tries reading again.
When the error is not recovered from, reading is retried repeatedly the number of
times specified in the MODE SELECT parameter ("Number of Retries during
Read" or "Number of Retries during Write").
In cases where correction is possible during execution of retry processing, the
processing procedure is according to "Correctable Data Read Error" in item (3).
If errors cannot be recovered from even after retry is executed the specified
number of times, the IDD terminates the command that is currently being
executed with a CHECK CONDITION status. The sense key in the sense data at
this time is "MEDIUM ERROR [=3]" and the ASC/ASCO indicates "Sync Mark
not found for data field [=13-00]" or "Unrecovered read error [=11-01]."
In this error retry processing, rereading accompanied by head offset processing is
performed.
(3) Correctable data read error
This error is a correctable ECC error when data are being read. Processing
methods when this error is detected differ depending on the values specified in the
EER flag and DCR flag in the MODE SELECT parameters.
If immediate correction of errors is permitted (DCR = 0, EER = 1), the IDD
immediately makes error corrections in the data buffer and sends the corrected
data to the INIT. Also, in the case of Verify processing, at the point when it
judges that correction is possible, it regards verification as being successful and
continues processing of subsequent data blocks.
If error correction is permitted but immediate correction is not permitted (DCR =
0, EER = 0), reading of data as in item (2) is retried up to the number of times
specified in the other MODE SELECT parameters ("Number of Retries during
Read" or "Number of Retries during Write").
If error correction is prohibited (DCR = 1, EER = 0), reading of data as in item (2) is
retried up to the number of times specified in "Number of Retries during Read" or
"Number of Retries during Write."
If the error cannot be recovered from even when this retry processing is executed,
the IDD terminates the command that is currently being executed with a CHECK
CONDITION status. The sense key in the sense data at this time is "MEDIUM
ERROR [=3]" and the ASC/ASCO indicates "Unrecovered read error [=11-00]."
C141-C009
5.3 Disk Drive Error Recovery Processing
5-25
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