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C141-E205 3-3
(1) User space
The user space is a storage area for user data. The data format on the user space (the length of data
block and the number of data blocks) can be specified with the MODE SELECT or MODE
SELECT EXTENDED command.
The user can also specify the number of logical data blocks to be placed in the user space with the
MODE SELECT or MODE SELECT EXTENDED command. When the number of logical data
blocks is specified, as many cylinders as required to place the specified data blocks are allocated in
the user space.
A number starting with 0 is assigned to each cylinder required in the user space in ascending order.
If the number of cylinders do not reach the maximum, the rest of the cylinders will not be used.
Always one cylinder is located at the end of each zone in the user space as an alternate cylinder.
Alternate cylinders will be used for alternate blocks. See Subsections 3.1.2 and 3.3.2 for details.
(2) Internal test space
The Internal test space is an area for diagnostic purposes only and its data block length is always
512KByte. The Internal test space consists of 8 cylinders and outer-host cylinder is always
assigned (Cylinder –147 to –154). The user cannot change the number of cylinders in the Internal
test space or their positions.
(3) System space
The system space is an area for exclusive use of the IDD itself and the following information are
recorded.
• Defect list (P list and G list)
• MODE SELECT parameter (saved value)
• Statistical information (log data)
• Controller control information
The above information is duplicated in several different locations for safety.
Note:
The system space is also called SA space.
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.