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 specified 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 subsequent sectors in the cylinder 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