Additional Information; Scsi Protocol; Priority Of Scsi Status Byte Reporting - IBM IC35L036UWDY10 - Ultrastar 36.7 GB Hard Drive Specifications

11.0 Additional information

This chapter provides additional information or descriptions of various functions, features, or operating
models supported by the Target that are not fully described in previous chapters.

11.1 SCSI Protocol

There are various operating conditions that prevent the Target from executing a SCSI command. This
section describes each of these operating conditions and their relative priority.

11.1.1 Priority of SCSI Status Byte Reporting

After establishing the I_T_L nexus or I_T_L_Q nexus the Target must first determine whether command
execution is allowed. Execution is deferred until a later time if the command must be added to the com-
mand queue. Execution may also be prevented by an internal Target condition that requires the reporting
of a CHECK CONDITION, QUEUE FULL, BUSY or RESERVATION CONFLICT Status. There are several
different internal conditions to be active at the same time. The order in which the Target checks for each of
these conditions determines their priority (highest priority first) as follows:
1. CHECK CONDITION status for invalid Logical Unit Number. See Section 11.1.2 , "Invalid LUN in
Identify Message" on page 194.
2. CHECK CONDITION status for Incorrect Initiator Connection. See Section 11.1.3 , "Incorrect Initiator
Connection" on page 194.
3. BUSY Status or QUEUE FULL Status. See Section 11.1.4 "Command processing during execution
of active I/O process" on page 194.
4. CHECK CONDITION status for UNIT ATTENTION condition. See Section 11.1.5 "Unit Attention
Condition" on page 196.
5. CHECK CONDITION status during Startup and Format operations. See Section 11.1.6 "Command
processing during startup and format operations" on page 197.
6. CHECK CONDITION status for Deferred Error Condition. See Section 11.1.7 , "Deferred Error" on
page 197.
7. RESERVATION CONFLICT status. See Section 11.1.9 , "Command processing while reserved" on
page 203.
8. CHECK CONDITION status for invalid command opcode
9. CHECK CONDITION status for invalid command descriptor block
The highest priority internal condition that prevents command execution is reported by theTarget if there is
no bus error.
For all CHECK CONDITION Sense data is built by the drive provided a valid LUN address is known.
Sense data is cleared by the Target upon receipt of any subsequent command to the LUN from the
initiator receiving the CHECK CONDITION.
Ultrastar 146Z10 hard disk drive specifications
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