96-277r1 - Proposed Change in QErr for SPC-2
PJohansson at aol.com
PJohansson at aol.com
Wed Feb 12 20:46:19 PST 1997
* From the SCSI Reflector (scsi at symbios.com), posted by:
* PJohansson at aol.com
Ralph et al,
Please see the comments embedded below:
In a message dated 97-02-12 16:24:14 EST, ROWEBER at acm.org writes:
<< To resolve this problem, it is proposed that the QErr bit become a two-bit
QErr field by extending QErr to include bit position 2 in byte 3 in the
Control mode page in SPC-2. The text defining the QErr field will be
constructed so that the existing meanings of QErr=0 and QErr=1 will be
preserved, with new meanings being assigned to QErr=10 and QErr=11. The
following definition of the new QErr field is proposed:
The queue error management (QErr) field specifies how the device server
shall handle blocked tasks when another task receives a COMMAND
TERMINATED or CHECK CONDITION status (see table n1).
Table n1 - Queue error management (QErr)
00b Blocked tasks in the task set shall resume after an ACA
condition is cleared (see SAM).
01b All the blocked tasks in the task set shall be aborted when
the COMMAND TERMINATED or CHECK CONDITION status is sent.
A unit attention condition (see SAM) shall be generated for
each initiator that had blocked tasks aborted except for
the initiator to which the COMMAND TERMINATED or CHECK
CONDITION status was sent. The device server shall set
the additional sense code to COMMANDS CLEARED BY ANOTHER
What applications are expected to use the QErr value of 01b?
<< 10b Reserved
11b Blocked tasks in the task set belonging to the initiator to
which a COMMAND TERMINATED or CHECK CONDITION status is
sent shall be aborted when the status is sent.
NOTE n2 In a multi-initiator configuration, QErr=01b can produce
looping repetitions of CHECK CONDITION status being sent to various of
the multiple initiators or service requests being timed out because
tasks are aborted and unit attention notification fails due to the
absence of new service requests.
It also must be noted that the proposed change in the definition of QErr
affects the already approved proposal defining the Basic queuing model
(96-198r4). So that the Basic queuing model can be functional in a
multi-initiator configuration, I propose that the previous Basic queuing
model approval be amended to use QErr=11b and its associated definition
above wherever 96-198r4 uses QErr=1.
It is not at all clear that this reinterpretation of QErr is in accordance
with the wishes of those who advocated (and voted for) the Basic queuing
model. I think the willingness to modify might be connected with your answer
to the question posed above.
The SBP-2 ad hoc working group is one of the significant constituencies for
the Basic queing model. We are meeting in Bothell, WA this Tuesday and
Wednesday and I will raise your concerns and suggestions tomorrow
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