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SCSI Description
Quantum DLT 7000 Tape System 3-11
CAUTION
Any occurrence of a bus parity error (i.e., a single-bit error) should
be considered serious: it implies the possibility of undetected
double-bit error may exist on the bus. This may cause undetected
data corruption. On properly configured SCSI buses, parity errors
are extremely rare. If any are detected they should be addressed by
improving the configuration of the SCSI bus. A well-configured SCSI
bus in a normal environment should be virtually free of bus parity
errors.
Bus parity errors cause the tape drive to retry the operation, go to
the STATUS phase, or go to BUS FREE and prepare Sense Data.
Retrying of parity errors during Data Out Phase when writing is
normally not done, but can be enabled by changing the
EnaParErrRetry parameter in the VU EEROM Mode Page. This feature
is not enabled by default because of possible negative impact on
device performance (the data stream on writes cannot be pipelined
as well).
Initiators normally do not expect the BUS FREE phase to begin because of the
drive’s release of the BSY signal unless it has occurred after the detection of a
reset condition or after a drive has successfully transmitted or received one of
the following messages:
Messages Transmitted from Drive:
• DISCONNECT
• COMMAND COMPLETE
Messages Received by Drive:
• ABORT
• BUS DEVICE RESET
• RELEASE RECOVERY