SCSI Interface Overview
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1. The command completes with a Check Condition and a 40h Sense data
indicating EOM and no Sense Key.
2. Subsequent WRITE commands write data and complete with check condition
with EOM Status and No Sense Key until the physical tape end is encountered.
2.7.8
Error Reporting
Soft errors are generally tape-quality related and occur more frequently during write
operations than during read operations. Soft errors indicate repeated attempts by
the drive to read or write data on the tape. Some soft errors are normal, but an
increase in the usual count can indicate deteriorating tape quality. If the soft error
count remains higher than normal, use a cleaning cartridge to clean the read/write
heads. If this procedure does not resolve the problem, change to a new data
cartridge.
If a hard error (unrecoverable error) occurs during operation, the drive terminates
operation immediately and returns a Check Condition. The Initiator should cease
any further read or write functions and issue a REQUEST SENSE Command to
determine the type of error.
When the drive detects a write error, it attempts to rewrite the data up to 128 times.
After the 128th attempt, the error is considered unrecoverable and the operation
terminates. When a hard error is encountered use a cleaning cartridge to clean the
read/write heads. If this procedure does not clear the problem, change to a new data
cartridge.
2.7.9
Variable and Fixed Mode Recording
The LTO drive can write either fixed or variable block sizes. The recording mode is
determined by the Fixed bit in the SCSI WRITE and READ commands.
If the Fixed bit is set, the MODE SELECT command sets the size of the next block
or multiple blocks to be written with the next WRITE command. When a WRITE
command is issued with the Fixed bit set, the current block size is implemented. The
transfer length specifies the number of blocks to be written with this size. If a WRITE
command is issued with the Fixed bit set and the current block size set to 0, the LTO
drive returns a Check Condition with Illegal REQUEST SENSE Key. When writing
with the Fixed bit set, each WRITE command specifies the number of contiguous
blocks to be written of a fixed size, resulting in fixed-mode blocks. If the Fixed bit is
reset, then only one block can be written on the tape per SCSI WRITE command
CDB. In that case, the WRITE command CDB transfer length specifies the size of
the block to be written in bytes. With the Fixed bit reset, the current block size
specified with the last MODE SELECT command is ignored.
Setting the block size to 0 in the MODE SELECT page descriptor is not required.
Therefore, with the Fixed bit reset, each SCSI WRITE command may specify a
different byte count, resulting in variable-mode blocks.
The host may switch between fixed and variable mode recording. By issuing the
MODE SELECT command to specify different block sizes, blocks can be written to
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