User Manual

SCSI Commands Reference Manual, Rev. J 70
www.seagate.com Direct Access Block commands (SPC-5 and SBC-4)
PARAMETER DATA LENGTH field
The parameter data length field specifies the length in bytes of the parameter data that shall be transferred from the application client to the
device server. A parameter data length of zero indicates that no data shall be transferred. This condition shall not be considered as an error.
Parameter data length values greater than zero indicate the number of bytes of parameter data that shall be transferred.
The parameter data is vendor-specific.
1) The parameter data may be used to specify a password to validate an operating definition change.
The CHANGE DEFINITION command causes one of the operating definition modifications listed below:
a) Change the operating definition of a logical unit relative to all initiators in the system: In this case, the target is capable of
maintaining a separate operating definition for each logical unit relative to all initiators in the system; or
b) Change the operating definition of all logical units in the target relative to all initiators in the system: In this case, the target is capable of
maintaining only one operating definition.
2) This manual does not provide a direct means to determine which of the above methods has been implemented. An
indirect means of determining which method is implemented exists in that the device server is required to inform affected
initiators of operating definition changes via the unit attention condition.
3) The modifications listed c) and d) above may result in incompatibilities if other initiators are using a different SCSI version.
The operating definition is modified after successful completion of the command. The application client should verify the new
operating definition by issuing an INQUIRY command requesting the implemented operating definition page (see SCSI -3).
4) The method of changing the operating definition is vendor-specific. Some implementations may require that the target’s
operating mode be reinitialized as if a power-up or hard reset had occurred. Other implementations may modify only
those operating definitions that are affected by the CHANGE DEFINITION command.
If the CHANGE DEFINITION command is not executed successfully for any reason, the operating definition shall remain the same
as it was before the CHANGE DEFINITION command was attempted. If it is impossible to return to the previous operating
definition, a unit attention condition shall be generated.
5) The present operating definition of the target may always be interrogated through the INQUIRY command. When an
SCSI-3 target has its operating definition changed to an older SCSI operating definition, certain changes are needed to
promote compatibility with preexisting older SCSI initiators.
After a power-on condition or a hard reset condition, the target shall set its initial operating definition of the device server(s) to
the last saved value (if saving is implemented), or its default value (if saving is not implemented).
CONTROL byte
The CONTROL byte is defined in Clause 2.2.7.