Comments on SAM rev 13
GOP at rchvmp3.vnet.ibm.com
Wed May 4 05:35:30 PDT 1994
Date: May,05 1994 X3T9.2/94- r0
To: X3T9.2 Committee (SCSI)
From: George Penokie (IBM)
Subject: Comments on SAM Rev 13
Note: Comments marked with an * what I consider to be
non-editorial issues, questions, etc..
1. Page 9 Section 2.1.23 - When does execution start? (e.g. On
a write command some or all of the data is moved across the
interface. Has the write command started execution or not?)
2. Page 11 - Pending Task should be defined in the glossary
3. Page 15-16 - Several of the entries in the symbols list do
not have any spaces between the second column and the third
4. Page 39 Section 3.7 1st paragraph after figure 17 near the end
of the paragraph there is an undefined cross-reference.
5. Page 42 - The heading 4.1 and the two lines following it are
duplicated on the top of page 43.
6. Page 44 - 1st paragraph after table 3 - The second to the
last sentence should have a cross-reference to clause 6.6.1.
7.*Page 44 - 1st paragraph after table 3 - This is the start of
the ACA description problems. There should be a statement in
this paragraph that says that if the ACA bit is zero the SCSI-2
rules for handing exception conditions shall be used by the
Target. No further definition is required and in fact the
definitions in clause 4.6.1 only confuse anyone who has
implemented CA in SCSI-2.
8. Page 46 - section 4.2 - command terminated paragraph - There
is a undefined cross-reference at the end of the first sentence.
9. Page 46 and other places throughout the document - Statuses
and messages have been changed from 'Queue' to 'Task Set'. Was
this change agreed to by the committee? If so OK if not it
should be voted on.
10. Page 50 list under entry b - There should be an 'or' between
11. Page 53 section 220.127.116.11 last paragraph - The first sentence
should be changed from 'the mode byte of the' to 'the control
byte of the'.
12. *Page 53 section 18.104.22.168 last paragraph - The statement
'shall be unconditionally cleared upon receiving the next command
from the faulted initiator' is not the behavior described in
SCSI-2 for this condition. (See comment number 7 for the
13. *Page 54 section 22.214.171.124 first paragraph last sentence - What
are the conditions for 'acceptance'? Where in the task set is
the command placed; is the task treated as a Head of Queue,
Simple, or Ordered task?? (See comment number 7 for the
14. *Page 54 section 126.96.36.199 2nd paragraph first sentence states
'The completion of the new task with'. I do not know what is
meant by 'new task' in that sentence. I assume it is an attempt
to reword the 2nd paragraph in section 2.1.1 of the SCSI-3
Queuing Model but the message seems to have been lost.
15. *Page 54 section 188.8.131.52 3rd paragraph first sentence should
be changed to 'faulting command, then the auto contingent
allegiance condition shall not be cleared and a new task shall be
entered into the..'
16. *Page 54 section 184.108.40.206 3rd paragraph last sentence: I have
not idea what this sentence means.
17. *Section 4.6.1: After careful study of this section there
seems to be several concepts defined in the SCSI-3 Queueing
Model that are not here. The Missing concepts are list below:
2.1.2 Response to Auto Contingent Allegiance Condition
If a Task becomes a current task because of a previous
request for information that information shall be suspended
until the ACA is cleared.
2.1.3 Auto Contingent Allegiance Processing
All SCSI operations are permitted while processing an ACA
2.1.4 Clear Auto Contingent Allegiance Task Management
The target shall clear the Auto Contingent Allegiance and
complete the current Task on acceptance of this task
If the target accepts a Clear Auto Contingent Allegiance
Task Management Function and no Auto Contingent Allegiance
Condition is in effect for that initiator on that task set,
then the target shall complete the current Task.
If a Clear Auto Contingent Allegiance Task Management
Function occurs when an ACA Task is pending then the ACA Task
shall be aborted and the auto contingent allegiance shall be
Attempted shall be used.h then an ASC of Overlapped Commands
18.* Page 54 section 4.6.2 last paragraph 2nd sentence should be
changed to '...tasks for the initiator that caused the overlapped
commands in the task set...'.
19. section 4.6.2 - The list of things that can occur to free up
tags is not listed. The list out of the SCSI-3 Queueing Model
2.2 Duplicate Tag Handling
When issuing a tagged task the initiator shall not
reuse the tag to create a new task until:
-A service response of Command Complete is received with a
status other than INTERMEDIATE or INTERMEDIATE-CONDITION
-A service response of Service Delivery or Target Failure is
received. In this case, system implementations shall
guarantee that the task associated with that command has
-A power on condition occurs.
-A Target Reset Task Management request occurs.
-An Abort Task Management request occurs.
-An Abort Task Set Management request occurs.
-A Clear Task Set Management request occurs.
-A unit attention of TASKS CLEARED BY ANOTHER INITIATOR is
-A unit attention of POWER ON, RESET or TARGET RESET is
20.* Page 58 section 4.6.5 - In this section it must me made
clear that the clearing of the unit attention condition does not
automatically clear the auto contingent allegiance condition if the
ACA bit is set to one.
21. Page 62 section 5.3 last paragraph - The last sentence should
be changed to ' ...subject to the task set management...' and the
wrong clause os referenced; it should reference clause 6.
22. *Page 67-74 sections 6.2 - 220.127.116.11 - I attempted to
understand this section to see if it matched the SCSI-3 Queueing
Model but I could not. The problems I had were:
-Cross-references in almost every sentence.
-Figure 23 is incomprehensible to me (Bring back the bubbles).
-The words previous and prior drive me crazy what's wrong with
simple words like before and after.
-Sections 6.3.1 to 18.104.22.168 are frustrating trying to understand.
To net it out: I cannot determine if SAM complies with the SCSI-3
Queueing Model. The only thing I can go by is section 6.5 which
contains the task management examples. Everything in the
examples looks correct except for one minor editorial change (see
below). But those are only examples and I cannot assume the
other sections correctly define the actions within the examples.
23. Page 76 figure 29 - The lower left task set brackets for the
enabled tasks should be extended to include the Head of Queue
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