Comments on SAM open issues

George Penokie GOP at rchvmp3.vnet.ibm.com
Thu Feb 10 09:43:32 PST 1994


 Subject: Open issues from January 11 SAM working group

 Ref: (a) X3T10/94-043R0 Results of 11 January, 1994 SAM Working Group Review

   >I have inserted my comments - George Penokie


 The purpose of this note is to request feedback on the following open
 issues from the last SAM working group review:

 1) Logical unit policy for automatic return of sense data.

 2) Logical unit response to a CLEAR ACA task management function
    while an ACA command is pending.


 Item 1: When must a target automatically return sense data?

 Assuming the protocol supports automatic return of sense data by a
 target (AKA 'autosense'), and the application client (i.e., the device
 driver) requests autosense information, when must the target return such
 information?

 a) If and only if a command terminates with a CHECK CONDITION or COMMAND
    TERMINATED status.

   This is what I consider the "right" way. Autosense should only be used to
   report error conditions that occur.

 b) Any time sense data is available after completion of a command,
    regardless of status. E.g., on the occurrence of a recovered error
    after a status of GOOD was returned.

 > Both the a and b options and possibly some other options will be
 > selectable in an SDA device using a Mode Page.  For non-SDA devices
 > I would consider the a option as the correct (as in this is the way
 > it has always been done) answer.

 I have no bias either way. However, I should mention that if the protocol
 does not support autosense, the behavior of alternative (a) can be
 easily simulated by host software (e.g., the CAM-SIM layer).
 Alternative B, on the other hand, cannot be simulated when sense data is
 unexpectedly generated by the logical unit.


 Item 2: After a contingent allegiance condition occurs, how should a
        logical unit respond to a CLEAR ACA task management function
        while an ACA command is pending?


 Alternative a) The CLEAR ACA task management function shall cause the
                ACA command to be aborted.

 Alternative b) The CLEAR ACA task management function shall not affect
                the pending ACA command. However, other pending commands
                may then complete.

  >The Queueing Model (92-141r8) currently defines alternative a as the
  >correct action.

 Thanks,
 Charles





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