Reading; Illegal Length Conditions When Reading - Tandberg Data SLR7-140 PROGRAMMER Manual

Tandberg Data
When the FIX bit is set to one, a WRITE command may
write multiple blocks. The WRITE command must specify
the number of blocks to write. All written blocks will
be of the same length. The block size is controlled by
the Block Size field in the MODE SELECT Block Descriptor
List. Depending on the tape format used, different fixed
block sizes are supported.
Note that when the Block Size field has been set to
zero, the Drive is said to be in Variable Block mode and
commands with the FIX bit set to one are not allowed.
2.6.3.

Reading

When reading data off a tape, the Drive is able to
determine the length of each block read. When reading,
the expected block length must be specified. This can be
done in two different
versions of the READ command; one with the fixed (FIX)
bit set and one with the fixed (FIX) bit clear.
When the FIX bit is clear, a READ command will read a
single block. The expected block length may be specified
on a block-by-block basis.
When the FIX bit is set to one, a READ command may read
multiple blocks.
number of blocks to read. The expected block length of
all blocks is the same. The expected length is specified
with the MODE SELECT command (the Block Size field of
the Block Descriptor List). Note that when the Block
Size field has been set to zero, the Drive is said to be
in Variable Block mode and commands with the FIX bit set
to one are not allowed.
2.6.4.

Illegal Length Conditions when Reading

When the specified
actual block length, the READ command will complain (if
the Suppress Illegal Length Indicator (SILI) bit was not
set in the READ Command Descriptor Block).
If the actual block length is smaller then the expected
block length, the READ command will transfer the actual
number of bytes found in the block. The READ command is
then terminated
Illegal Length Indicator will be set in the Sense Data
List. If the fixed-bit is cleared, the Information Bytes
will be set to
number of bytes and the actual number of bytes. This
will be a positive number in this case. If the fixed-bit
is set, the Information
difference between the specified number of blocks and
the actual number of blocks transferred. The block with
the unexpected length is counted among the transferred
blocks even if its length was wrong. Note that this
means that the Information Bytes may read zero even if
the READ command was terminated with CHECK CONDITION and
Illegal Length
will be at the beginning of the next block on the tape.
2-18 Tandberg SLR Product Line SCSI Functional Specifications
ways with
The READ command
block length
with a CHECK
the difference
Bytes
Indication. The
About Tape Streamers
the two different
must specify
does not match
CONDITION Status.
between the expected
will be set to
logical tape position
the
the
The
the