Proposed Change to Specify QErr Support Requirements

Charles Monia Monia at
Thu May 1 23:03:02 PDT 1997

* From the SCSI Reflector (scsi at, posted by:
* Charles Monia <Monia at>
Date:	2 May, 1997

From:	Charles Monia
	Digital Equipment Corporation

To:	Members of X3T10

Subject: Proposed Change to Specify QErr Requirements

Proposal X3T10/96-277r2, which was passed by the Committee at the March
Plenary, added a new QErr behavior to resolve a multi-initiator CHECK
CONDITION deadlock.  In doing so, the proposal, as passed deleted the
requirements defining what QErr behaviors shall be supported by a device
implementing command queuing.

During the subsequent working group discussion, there appeared to be
agreement among device vendors and systems integrators that values of 00
or 11 were acceptable and that at least one of these could be
implemented by all devices, regardless of the type of queuing supported.
 However, since agreement on precise wording could not be obtained, the
proposal as passed directed that the requirements for QErr behavior be
deleted from the Basic Queing Model.

This proposal addresses that deletion by modifying X3T10/96-272r2 to
replace the last sentence with the following:

"Devices that implement any of the command queuing behaviors defined in
this standard shall support at least one of the queue error management
policies specified above and may optionally support more than one. In
any case, at least one of the supported policies shall implement QErr
behavior corresponding to a value of either 00h or 11h".

*   Charles Monia, Storage Architecture Group              *
*   M/S SHR3-2/C5
*   Digital Equipment Corporation                                   *
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