HP Surestore 28/48-Slot with DLT7000 Digital Linear Tape SCSI-2 Drive and SCSI - Page 42

SCSI Command Overview Library Control Commands The Test Unit Ready command is used to determine whether the tape drive accepts a Media Access command without returning CHECK CONDITION. Bus Free Condition There are several situations when the device might or will go to BUS FREE unexpectedly, as defined in the SCSI-3 standard: • An internal hardware or firmware fault that makes it unsafe for the device to continue operating without a full reset (similar to a power up reset) • An ATN asserted or bus parity error during non-tape data transfers Bus Parity Error Condition The occurrence of bus parity errors (single bit errors) are rare and very serious since they imply the possibility of undetected double-bit errors on the bus, which could result in undetected data corruption. On properly configured SCSI buses, parity errors should be extremely rare. If detected, immediately take steps to improve the SCSI bus configuration. Bus parity errors cause the library to do the following: • Retry the operation • Go to the Status phase • Go to Bus Free and prepare Sense Data Other SCSI Functionality • Linked commands are not supported. • Untagged queuing is supported. 1- 18 Chapter 1