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C141-E124-01EN 6 - 3
• Alternate block allocation processing during FORMAT UNIT command execution
With the FORMAT UNIT command, alternate block allocation is done by sector slip
processing until all the spare sectors within the same cylinder have been used up for
defective sectors included in the type of defect list (P, G or D) specified in the command.
When all the spare sectors in the same cylinder have been used up, subsequent defective
sectors in that cylinder are treated by allocating spare sectors in an alternate cylinder by
alternate sector processing.
After implementing this alternate block allocation and initializing the disk media, at times
when a data block Verify (Certification) operation is not prohibited, the IDD, reads all the
initialized data blocks and verifies their normalcy. If a defective data block is detected
during this processing, the IDD generates the C List as defect position information and
allocates alternate blocks by alternate sector processing for those defective data blocks.
In this case, if there are any unused spare sectors in the same cylinder as the defective
data blocks, alternate blocks are allocated within the same cylinder, but if the spare
sectors are all used up in the same cylinder, alternate blocks are allocated in spare sectors
in an alternate cylinder.
• Alternate block allocation processing by the REASSIGN BLOCKS command
With the REASSIGN BLOCKS command, alternate block allocation is performed by
alternate sector processing for defective logical data blocks specified by the INIT. In this
case, if there are unused spare sectors in the same cylinder as the specified defective
logical data blocks, alternate block allocation is done within the same cylinder, but if all
the spare sectors in the same cylinder have been used up, alternate blocks are allocated in
spare sectors in an alternate cylinder.
• Auto alternate block allocation processing
If auto alternate block allocation processing is permitted by the AWRE flag or the ARRE
flag of the MODE SELECT parameters, the IDD executes alternate clock allocation
automatically by alternate sector processing for defective data blocks detected during
execution of the WRITE, WRITE EXTENDED, WRITE AND VERIFY, READ and
READ EXTENDED commands. The alternate block allocation method in this case is the
same as in the case of the REASSIGN BLOCKS command. See the description in
Section 5.3.2 concerning "Auto Alternate Block Allocation Processing".