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If a "Header," "Block Descriptor" or any "Page Descriptor" cannot be transferred with all the
defined length because the total defined length of the MODE SELECT parameters actually
transferred from the INIT do not match the value specified in the "Parameter List Length"
field, or if the total of the MODE SELECT parameter's defined length transferred from the
INIT exceeds the value specified in the "Parameter list length" field, this command is
terminated with a CHECK CONDITION status (ILLEGAL REQUEST [=5] / Invalid field in
CDB) [=24-00], and all the MODE SELECT parameters transferred in the command are
disabled.
Three types of values exist in the MODE SELECT parameters, "Current," "Save" and
"Default" values. "Current" values are parameters which actually control the IDD's operation,
and the parameters specified by this command are converted to "Current" values. "Save"
values are parameter values specified by this command which are preserved on the disk. And
"Default" values are values which the IDD uses as "Current" values during the time until
reading of "Save" values is completed after the IDD's power is switched on, or when no
"Save" values exist and no MODE SELECT command is being issued.
The IDD has a common set of "Current", "Save" and "Default" values of all the MODE
SELECT parameters for all the INITs.
When the IDD's power is switched on, when a RESET condition occurs or when the IDD
receives a BUS DEVICE RESET message, the "Current" MODE SELECT parameter values
are changed to the "Save" parameter values, if they exist, and are changed to the "Default"
parameter values if the "Save" values do not exist.
When any of the parameters related to the data format on the disk media (Block Descriptor,
Format parameters: Page 3, and Drive parameters: Page 4), parameters related to the segment
buffer (Caching parameters: Page 8, byte 13) and parameters related to command queuing
(Control mode parameters: Page A, byte 3, D Que) is changed by this command, a UNIT
ATTENTION condition (Mode parameters changed [=2A-01] is generated for all the INITs
other than the INIT that issued this command.
When the RESERVE command is issued which specifies the Third Party Reserve function, the
"Current" values of MODE SELECT parameters of the INIT that issued the RESERVE
command are copied to "Current" values for a third party device specified by the RESERVE
command. Details of this function are described in 3.1.11, "RESERVE (16)."
The relation between the three types of parameters, "Current," "Save" and "Default," is shown
in the following diagram.
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C141-E039-01EN
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