X3T9.2/89-024 January 24, 1989 To: X3T9.2 From: John Lohmeyer, NCR Corporation Subj: When not to clear sense data I had an interesting phone call from a user of a SCSI device. He was testing the effect of induced parity errors on a SCSI device, which will remain nameless. When a parity error was induced during the DATA IN phase of a REQUEST SENSE command, this person's host adapter correctly sent an INITIATOR DETECTED ERROR message to the target. The target responded with MESSAGE REJECT message, ended the REQUEST SENSE command, and cleared the sense data. This does not precisely violate the standard, but it sure is not friendly. I propose that we revise the pertinent paragraph in the REQUEST SENSE command description as shown below: REPLACE: The sense data shall be preserved by the target for the initiator until retrieved by the REQUEST SENSE command or until the receipt of any other command for the same I_T_x nexus (see 6.6). Sense data shall be cleared upon receipt of any subsequent command (including a REQUEST SENSE) to the I_T_x nexus. WITH: The sense data shall be preserved by the target for the initiator until successfully transferred by the REQUEST SENSE command or until the receipt of any other command for the same I_T_x nexus (see 6.6). Sense data shall be cleared upon receipt of any subsequent command to the I_T_x nexus or upon successful completion of a REQUEST SENSE command to the I_T_x nexus. Sense data shall not be cleared if the REQUEST SENSE command does not complete with GOOD status.