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30 C141-E252
3.1.2 Alternate spare area
The alternate spare area consists of the last track of each cell in the user space and an alternate
cylinder allocated to the last 10 cylinders of the last zone in the user space.
The spare area in each cell is placed at the end of the last track as shown in Figure 3.2. These spare
sectors are located in the end of the track logically, not necessarily located at the end physically
because of track skew or cylinder skew. (Details are explained on Subsection 3.1.3.)
Size can be specified by the MODE SELECT command.
The number of spare sectors per cell is fixed at 300. This number cannot be changed by users.
SPR299 SPR300
300
Note:
This HDD manages alternate spare areas for each cell, which is a set of cylinders. One cell
consists of 40 cylinders.
Figure 3.2 Spare area in cell
The alternate cylinder is used for replacement action via the REASSIGN BLOCKS command or
automatic replacement processing. The alternate cylinder is allocated to 10 cylinders at the end of
the last zone in the user space.
Note:
The number of alternate cylinders cannot be changed.
Figure 3.3 Alternate cylinder
Cell