Unit Attention and Reservation Conflict

Chuck Gibson cgibson at sisa.samsung.com
Thu Oct 5 14:14:00 PDT 1995

I checked out the drives that I had on the bench. The IBM and Samsung drives
returned Check Condition-UA on the first command, then a Reservation 
on subsequent commands.
The Quantum (XP32150) gave a Reservation Conflict until the reservation was
cleared, then responded with Check Condition-UA.
My personal preference is for the Quantum method, since Reservation Conflict
does have a higher priority...
From: sgaskill
To: scsi
Subject: Unit Attention and Reservation Conflict
Date: Thursday, October 05, 1995 10:58AM

Based on section 7.9 in SCSI-2 rev 10K (second half of section) it is 
to what action the target should take in the following situation.

1. Target has a pending Unit Attention condition for all initiators.
2. Initiator A selects the target, gets the Unit Attn, and then creates a
"normal" reservation (not 3rd party, not "persistent").
3. Initiator B issues a Test Unit Ready to the target and gets the
Conflict (higher priority status as noted in 7.9).
4. Initiator A releases the reservation.
5. Initiator B issues another Test Unit Ready to the target.

Q: Will Initiator B get a Unit Attention OR should the UA condition have 
cleared by the TUR which resulted in a reservation conflict?

Alternate question:  What do most peripherals do in this situation?

Thanks very much for the help.

  Steve Gaskill
  Quantum Corp

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