Comments on SAM rev 13

[George Penokie]

     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
     column.

     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
     RESET,
     TARGET RESET.

     11. Page 53 section 4.6.1.1 last paragraph - The first sentence
     should be changed from 'the mode byte of the' to 'the control
     byte of the'.

     12. *Page 53 section 4.6.1.1 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
     solution.)

     13. *Page 54 section 4.6.1.1 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
     solution)

     14. *Page 54 section 4.6.1.1 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 4.6.1.1 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 4.6.1.2 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
       Task.

       2.1.4 Clear Auto Contingent Allegiance Task Management
             Function

       The target shall clear the Auto Contingent Allegiance and
       complete the current Task on acceptance of this task
       management function.

       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
       cleared.
       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
     follows:

       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
        MET.
       -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
        been terminated.
       -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
        reported.
       -A unit attention of POWER ON, RESET or TARGET RESET is
        reported.

     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 - 6.4.4.1 - 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 6.3.8.1 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
     (Task 7).