IBM IC35L036UWDY10 Hard Drive Specifications - Page 220

Priority commands, 3 Command queuing

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3. If the issuing initiator is the one that made the reservation but is not the one to receive the reservation, ! A REQUEST SENSE, INQUIRY, REPORT LUNS, LOG SENSE, READ CAPACITY, REPORT DEVICE IDENTIFIER or START STOP UNIT with START bit is permitted. ! Any other command results in a RESERVATION CONFLICT Status 4. If the issuing initiator is not the one that made the reservation but is the one to receive the reservation, ! A RESERVE command results in a RESERVATION CONFLICT Status ! A RELEASE command is permitted but is ignored ! Any other command is permitted If a RESERVATION CONFLICT Status is not reported and the command is permitted, then the Target checks the next highest priority internal condition to determine whether execution is allowed. See Section 11.1.1 , "Priority of SCSI Status Byte Reporting" on page 193 11.2 Priority commands The following SCSI commands known as Priority Commands always execute without returning a BUSY Status or RESERVATION CONFLICT Status. ! INQUIRY ! REQUEST SENSE ! REPORT LUNS These commands do not disconnect from the SCSI bus prior to completion. They are executed prior to attempting to complete the execution of any other pending command that has disconnected from the SCSI bus. Therefore, a second priority command cannot be received during the execution of a priority command. These commands are never queued whether or not the command is sent with a queue tag. However, the rule for an Incorrect Initiator Connection still apply to priority commands. See Section 11.1.3 , "Incorrect Initiator Connection" on page 194. 11.3 Command queuing When the initiator specifies that the drive shall disable command queuing, the initiator must send only untagged commands. When the initiator specifies that the drive shall enable command queuing, the initiator may send either tagged or untagged command, but shall not use both at the same time. The following commands are never queued and will be immediately executed without Bus disconnection: ! Priority Commands ! Commands linked to previous commands. These are defined to be part of a single I/O process. (Linked commands are always executed immediately following the previous command from the same initiator. No other Initiator's command is allowed to be executed between two linked commands.) ! Commands for which disconnection is not allowed. (These may result in a BUSY Status.) ! Commands in which a SCSI bus error occurred between SELECTION and first disconnection following the receipt of the CDB. ! Commands for an invalid LUN. Ultrastar 146Z10 hard disk drive specifications 204

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3.
If the issuing initiator is the one that made the reservation but is not the one to receive the
reservation,
!
A REQUEST SENSE, INQUIRY, REPORT LUNS, LOG SENSE, READ CAPACITY, REPORT
DEVICE IDENTIFIER or START STOP UNIT with START bit is permitted.
!
Any other command results in a RESERVATION CONFLICT Status
4.
If the issuing initiator is not the one that made the reservation but is the one to receive the
reservation,
!
A RESERVE command results in a RESERVATION CONFLICT Status
!
A RELEASE command is permitted but is ignored
!
Any other command is permitted
If a RESERVATION CONFLICT Status is not reported and the command is permitted, then the Target
checks the next highest priority internal condition to determine whether execution is allowed. See
Section 11.1.1 , “Priority of SCSI Status Byte Reporting" on page 193
11.2 Priority commands
The following SCSI commands known as Priority Commands always execute without returning a BUSY
Status or RESERVATION CONFLICT Status.
!
INQUIRY
!
REQUEST SENSE
!
REPORT LUNS
These commands do not disconnect from the SCSI bus prior to completion. They are executed prior to
attempting to complete the execution of any other pending command that has disconnected from the SCSI
bus. Therefore, a second priority command cannot be received during the execution of a priority com-
mand.
These commands are never queued whether or not the command is sent with a queue tag. However, the
rule for an Incorrect Initiator Connection still apply to priority commands.
See Section 11.1.3 , “Incorrect
Initiator Connection" on page 194.
11.3 Command queuing
When the initiator specifies that the drive shall disable command queuing, the initiator must send only
untagged commands. When the initiator specifies that the drive shall enable command queuing, the initi-
ator may send either tagged or untagged command, but shall not use both at the same time.
The following commands are never queued and will be immediately executed without Bus disconnection:
!
Priority Commands
!
Commands linked to previous commands. These are defined to be part of a single I/O process.
(Linked commands are always executed immediately following the previous command from the same
initiator. No other Initiator's command is allowed to be executed between two linked commands.)
!
Commands for which disconnection is not allowed. (These may result in a BUSY Status.)
!
Commands in which a SCSI bus error occurred between SELECTION and first disconnection
following the receipt of the CDB.
!
Commands for an invalid LUN.
Ultrastar 146Z10 hard disk drive specifications
204