UA interlock & multiple initiators

Mallikarjun C. cbm at
Thu Feb 20 11:50:05 PST 2003

* From the T10 Reflector (t10 at, posted by:
* "Mallikarjun C." <cbm at>
Ed,  Thanks for the note.

I recall starting from SAM-3 - a quick search for "UA interlock" or "interlock"
did not yield any matches, and clause 5.9.7 that discusses Unit Attention wasn't
specific on this either.  But I now see that I should have searched for UA_INTLCK_CTRL.
I can now see that SAM-3 is defining the precise semantics of this bit field  - so at 
this point, my only recommendation would be to move the definition of those semantics 
|from the Status clause (5.3) to 5.9.7, or at least add a cross-reference from the latter.


Mallikarjun Chadalapaka
Networked Storage Architecture
Network Storage Solutions
Hewlett-Packard MS 5668 
Roseville CA 95747
cbm at

----- Original Message ----- 
From: "Edward A. Gardner" <eag at>
To: "Mallikarjun C." <cbm at>
Cc: "T10 Reflector" <t10 at>
Sent: Thursday, February 20, 2003 9:47 AM
Subject: Re: UA interlock & multiple initiators

> The intent was that a UA interlock would only be for the individual I_T_L 
> nexus that had a failed command.  That is, your "latter" case.
> Please check SAM-3.  SPC-3 only states the mechanism for enabling / 
> disabling UA interlock.  SPC-3 is not supposed to describe how it 
> works.  That is in SAM-3 (and under the principle of specifying things in 
> one place, should not be redundantly specified in SPC-3).  If you think 
> SAM-3 is ambiguous or unclear, we'll fix it.
> At 16:43 14-02-2003, Mallikarjun C. wrote:
> >* From the T10 Reflector (t10 at, posted by:
> >* "Mallikarjun C." <cbm at>
> >*
> >In looking through SPC-3 r09 for UA interlock (clause 8.4.6, table 223)
> >semantics, we couldn't find the answer to this question:
> >
> >When UA interlock is enabled (UA_INTLCK_CTRL = 11b), does the
> >device server establish a interlocked-UA condition for all initiators, or just
> >for the initiator whose task just terminated with BUSY/TASK SET FULL/
> >
> >I am thinking that it's the latter - i..e the interlocked UA is 
> >established only for
> >the I_T nexus that just had a failed command - because I could not come up 
> >with
> >a rationale for stalling all other initiators.  SPC-3 however, is not 
> >explicit about it.
> >
> >Comments?
> >--
> >Mallikarjun
> >
> >Mallikarjun Chadalapaka
> >Networked Storage Architecture
> >Network Storage Solutions
> >Hewlett-Packard MS 5668
> >Roseville CA 95747
> >cbm at
> Edward A. Gardner               eag at
> Ophidian Designs                719 593-8866 voice
> 1262 Hofstead Terrace           719 210-7200 cell
> Colorado Springs, CO  80907

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