User Manual

SCSI Commands Reference Manual, Rev. J 93
www.seagate.com Direct Access Block commands (SPC-5 and SBC-4)
ALLOCATION LENGTH field
The ALLOCATION LENGTH field is defined in 2.2.6. If EVPD is set to zero, the allocation length should be at least five, so that the ADDITIONAL
LENGTH field in the parameter data (see 3.6.2) is returned. If EVPD is set to one, the allocation length should be should be at least four, so that
the PAGE LENGTH field in the parameter data (see 5.4) is returned.
In response to an INQUIRY command received by an incorrect logical unit, the SCSI target device shall return the INQUIRY data
with the peripheral qualifier set to the value defined in 3.6.2. The INQUIRY command shall return CHECK CONDITION status only
when the device server is unable to return the requested INQUIRY data.
If an INQUIRY command is received from an initiator port with a pending unit attention condition (i.e., before the device server
reports CHECK CONDITION status), the device server shall perform the INQUIRY command and shall not clear the unit attention
condition (see SAM-5).
The INQUIRY data should be returned even though the device server is not ready for other commands. The standard INQUIRY
data should be available without incurring any media access delays. If the device server does store some of the standard
INQUIRY data or VPD data on the media, it may return ASCII spaces (20h) in ASCII fields and zeros in other fields until the data is
available from the media.
The INQUIRY data may change as the SCSI target device and its logical units perform their initialization sequence. (E.g., logical
units may provide a minimum command set from nonvolatile memory until they load the final firmware from the media. After
the firmware has been loaded, more options may be supported and therefore different INQUIRY data may be returned.)
If the INQUIRY data changes for any reason, the device server shall establish a unit attention condition for the initiator port
associated with every I_T nexus (see SAM-5), with the additional sense code set to INQUIRY DATA HAS CHANGED.
The INQUIRY command may be used by an application client after a hard reset or power on condition to determine the device
types for system configuration.