3.3 Defect Management
(1) Alternate block allocation during FORMAT UNIT command execution
When the FORMAT UNIT command is specified, the allocation of the alternate block to those
defective sectors included in the defect lists (P, G, or D) is continued until all spare sectors in the
same cell are used up. When they are used up, unused spare sectors in the alternate cylinder are
allocated to the defective sectors that follow the sector by means of alternate sector treatment.
Figure 3.7 is examples of the alternate block allocation during the FORMAT UNIT command
execution.
: n represents a logical data block number
: Defective sector
: Unused spare sector
Figure 3.7 Alternate block allocation by FORMAT UNIT command
During FORMAT UNIT command, alternate block allocation is conducted in following cases:
1) Unrecovered write offtrack condition during a media write
2) Uncorrectable Data Error during a media read (certification) *1
C141-E266 37
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