User's Guide

Commands: Read (08h) Page 107
Transfer Length Satisfied
If the CDB Transfer Length is satisfied, the command completes successfully with a
Good Status, and the tape is positioned on the EOT side of the last block read.
End of Tape (EOT) or End-of-Partition (EOP)
When the end-of-tape or end-of-partition position is encountered, the command
terminates with a Check Condition and Medium Error (03h) sense key. The Valid bit
(byte 0, bit 7) and the EOM bit (byte 2, bit 6) are set.
The Residual Length field is then set as follows:
• If the Fixed bit is 1, it equals the difference between the CDB transfer length and
the number of actual blocks read.
• If the Fixed bit is 0, it equals the CDB transfer length.
The logical position after encountering an end-of-tape or end-of-partition error is
undetermined.
Recoverable Data Error
If an error is encountered while reading, the read retry count (in the MODE SELECT
Read/Write Error Recovery page) specifies the maximum number of attempts to
reread the data. If none of the rereads are successful, the error is considered
unrecoverable and is reported as such. The drive might require as much as six
minutes to complete its error recovery procedure.
Unrecoverable Data Error
If an Unrecoverable Data Error is encountered, the READ command terminates with
Check Condition and a Medium Error (03h) sense key.
If the Valid bit (byte 0, bit 7) is set, Residual Length field equals the difference
between the requested Transfer Length and the actual number of blocks or bytes
transferred.
Incorrect Length
Reading fixed- and variable-length blocks varies according to the setting of the
Fixed bit.
When the Fixed bit is set (1), one or more tape blocks can be read. The CDB
Transfer Length field specifies the block count to read. The block size is the current
block size of the drive, which is set to 512 at power-up or after a SCSI Bus Reset.
The host can change the current block size by issuing a MODE SELECT command
with a new block descriptor parameter that specifies a new block size. If the current
block size differs from the actual block size of the block being read, the drive reports
an Incorrect Length error.
When the Fixed bit is reset (0), the CDB Transfer Length field indicates the number
of bytes to be read. When the actual block size found on tape differs from the CDB
Transfer Length, an Incorrect Length error is reported.
The drive reports the Incorrect Length error based on the Suppress Incorrect Length
Indicator (SILI) bit as follows: