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6.2 Disk Media Initialization
C141-E167 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 cell 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 cell have been used up, subsequent defective sectors in that
cell are treated by allocating spare sectors in an alternate cell 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 cell as the defective data blocks,
alternate blocks are allocated within the same cell, but if the spare sectors are all used up in
the same cell, alternate blocks are allocated in spare sectors in an alternate cell.
• 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 cell as the specified defective logical data
blocks, alternate block allocation is done within the same cell, but if all the spare sectors in
the same cell have been used up, alternate blocks are allocated in spare sectors in an
alternate cell.
• 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".
6.2 Disk Media Initialization
6.2.1 Initialization during installation
The disk drive is initialized for the inherent (default) data format for each respective model name
(model class) when it is shipped from the factory, so ordinarily, it is not necessary to initialized
(format) the disk media when it is installed in a system. However, in cases where data attributes
which differ from the default format are necessary, initialization (formatting) of the entire disk media
by the following procedures is necessary. At this time, the INIT can change the following data
format attributes.
• The logical data block length.
• The number of logical data blocks or the number of cylinders in the User Space.
• The size of the spare area for alternate blocks.