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C141-E056-02EN 6 - 11
6.4.1 Spare area
Following two types of spare area are provided in the user space.
1) Spare sector for sector slip:
used for alternating defective sectors at formatting in shipment in case that a physical track
contains one or two defective sectors (2 sectors/track)
2) Spare cylinder for track slip:
used for alternative assignment for the third and subsequent defective sectors in case that a
physical track contains three or more defective sectors, and also used by automatic
alternative assignment (78 cylinders/drive).
3) Spare cylinder for alternative assignment:
used for automatic alternative assignment (1 cylinder/drive).
6.4.2 Alternating defective sectors
The two alternating methods described below are available:
(1) Sector slip processing
A defective sector is not used and is skipped and a logical sector address is assigned to the
subsequent normal sector (physically adjacent sector to the defective sector).
When defective sector is present, the sector slip processing is performed in the formatting.
Figure 6.7 shows an example where (physical) sector 5 is defective on head 0 in cylinder 0.
21
Index
Head 0
Defective
sector
If an access request to sector 5 is specified, the device accesses physical sector 6 instead of sector 5.
Sector (logical)
Sector (physical)
Cylinder 0
43 65
297
30029929887
21 43 65 7
299298
Figure 6.7 Sector slip processing
243242
242
241
240
241
SP
unused