Incorporating Dual Port proposal into SAM

Gerry Houlder Gerry_Houlder at
Fri Aug 12 08:59:00 PDT 1994

>Gerry Houlder's comments ... are confusing to me.  I thought SAM
>said the "task set" was put into contingent allegiance (CA).  The task set
>defined by SAM is per logical unit, not per initiator/logical unit.  How can
>CA be on a "per inititator" basis as Gerry suggests?
>Charles Binford
A contingent allegiance actually applies to a single command. It is true that
the entire task set is supposed to be frozen until the contingent allegiance
between the initiator/LUN is cleared. The task set can include commands from
other initiators, but none of those commands are affected by the contingent
allegiance for that other initiator except that their execution may be delayed
while the other initiator clears its contingent allegiance.
I don't see any words in SAM that explicitly state this, but this is how SCSI-2
is today and I don't think we intended to change it. It would be appropriate to
add wording stating that an auto contingent allegiance condition exists for an
initiator/LUN combination. We didn't intend that initiators other than the one
that sent the "failing command" can send ACA commands to a LUN that has an
outstanding ACA condition, did we?
Gerry Houlder -- Gerry_Houlder at
Seagate Technology   -   920 Disc Drive   -   Scotts Valley, CA 95066 USA
Main Phone 408-438-6550   -   Email Problems postmaster at
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### OGATE Version 8 message trace and attachment information:
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### Org Date:    08-12-94 08:25:06 AM
### From:        Gerry Houlder at SEAGATE
### To:          scsi @ WichitaKS.NCR.COM @ internet
### Subject:     Re: Incorporating Dual Port proposal into SAM
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