SSC-4: Intent to obsolete READ POSITION data PERR bit

Ballard, Curtis C (StorageWorks) curtis.ballard at hp.com
Wed Mar 7 14:23:36 PST 2012


* From the T10 Reflector (t10 at t10.org), posted by:
* "Ballard, Curtis C (StorageWorks)" <curtis.ballard at hp.com>
*
The SSC-4 working group recently approved a change to how a device server
reports position information when the logical object location is a larger
number than is able to be reported in the logical object location field.
The old method was to set the PERR bit in the return data to one and the
application client was required to use that bit to determine whether the
return data was valid.
The new method terminates the command with CHECK CONDITION status and a new
additional sense code of TOO MANY LOGICAL OBJECTS ON PARTITION TO SUPPORT
OPERATION.
An application client could miss checking the PERR bit and attempt to use
invalid position information but can't miss the command terminating with
CHECK CONDITION.
Because the command will now terminate with CHECK CONDITION status in the
only condition where PERR could be set to one the function provided by that
bit is no longer necessary and the working group has proposed making that bit
obsolete.
Please respond to this message if you have any concerns with the plan to
obsolete the PERR bit.
Curtis Ballard
Hewlett Packard
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