Unit Attention with multiple LUNs?

Brian_Moyle at asd.sel.sony.com Brian_Moyle at asd.sel.sony.com
Wed Nov 20 16:47:37 PST 1996

* From the SCSI Reflector (scsi at symbios.com), posted by:
* Brian_Moyle at asd.sel.sony.com
I have been discussing the following question with one of my 
colleagues.  We are unsure of the correct SCSI response for the 
following scenario.

In an autoloader that can accept move medium commands to either LUN 0 
or LUN 1, how should the Unit Attention conditions be handled after a 
move medium command?  We feel the following is the appropriate 
response, regardless of the command, but we're not sure if it's 
consistent with the SCSI-2 specification (section 7.9, "Unit 
attention condition"):

    cmd issued       LUN(s)  
      to LUN        affected       UA for LUN0?     UA for LUN1?
   ------------   -------------   --------------   --------------
        0               0               NO               NO
        0             0,1               NO              YES
        0               1               NO              YES

        1               0              YES               NO
        1             0,1              YES               NO
        1               1               NO               NO

Is this correct?  In other words, is it okay to assume that an 
initiator remembers the last command it sent to a LUN and that it 
does not need additional reminding with a Unit Attention?

The SCSI-2 specification, if read conservatively, seems to indicate 
something different:

    cmd issued     cmd affects
      to LUN          LUN(s)       UA for LUN0?     UA for LUN1?
   ------------   -------------   --------------   --------------
        0               0              YES              YES
        0             0,1              YES              YES
        0               1              YES              YES

        1               0              YES              YES
        1             0,1              YES              YES
        1               1              YES              YES

Is this second method preferred?


Brian Moyle
Advanced Storage Development/Sony Electronics Inc.
Mail Drop: SJ-3B2
3300 Zanker Road
San Jose, CA 95134-1940
Phone: 408-955-5698
Fax:   408-955-5066
e-mail: Brian_Moyle at asd.sel.sony.com

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