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SCSI Description
3-12
Quantum DLT 8000 Tape System
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
•
ABORT TAG
•
CLEAR QUEUE
If an initiator detects the release of the BSY signal by the drive at any other time, the
drive is indicating an error condition to the initiator. The drive can perform this
transition to the BUS FREE phase independently of the state of the ATN signal. The
initiator manages this condition as an unsuccessful I/O process termination. The drive
terminates the I/O process by clearing all pending data and status information for the
affected nexus. The drive can optionally prepare sense data that can be retrieved by a
REQUEST SENSE command.
Bus Free Sequence
1.
BSY and SEL signals are continuously false for one bus settle delay.
2.
SCSI devices release all SCSI bus signals within one bus clear delay.
Summary of Contents for DLTtape DLT 8000
Page 1: ...DLTTM 8000 Tape System Product Manual Nov 10 2003 81 60118 06...
Page 5: ...USER MANUAL STATEMENTS FOR CLASS B EQUIPMENT continued...
Page 6: ......
Page 26: ...Table of Contents xxiv Quantum DLT 8000 Tape System...
Page 36: ...About This Manual Quantum DLT 8000 Tape System xxxii...
Page 54: ...General Description and Specifications 1 18 Quantum DLT 8000 Tape System...
Page 102: ......
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Page 376: ...Appendix A Definition of Vendor Unique Sense Data Information A 4 Quantum DLT 8000 Tape System...
Page 386: ...Appendix C Updating the Firmware C 6 Quantum DLT 8000 Tape System...
Page 396: ...Appendix E Visual Inspection Procedure for DLTtape Cartridges E 8 Quantum DLT 8000 Tape System...
Page 406: ...Appendix G DLT 7000 Emulation Feature G 8 Quantum DLT 8000 Tape System...
Page 407: ......