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3-4 C141-E237
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 cylinder of each zone.
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 can be specified from 0 to 200. The default for the spare sectors
number is 200.
Note: This drive manages alternate spare areas for each cell, which is a set of cylinders. One cell
consists of 27 cylinders.
Figure 3.2 Spare area in cell
An alternate cylinder is used when spare sectors in a cell are used up or 0 is specified as the number
of spare sectors in a cell. 1 cylinder at the end of each zone of the user space is allocated as alternate
cylinders as shown in Figure 3.3.
The user space and the CE space share the alternate cylinders.
Zone
Note: The number of alternate cylinders cannot be changed.
Figure 3.3 Alternate cylinder
Cell