Tandberg Data
Read
17-5
Tandberg SLR Product Line SCSI Functional Specifications
Fixed Block Mode
When the Block Size field in the Block Descriptor
List of the MODE SELECT command is different from
zero (Fixed Block mode), the READ command will then
be terminated with CHECK CONDITION status if the
Transfer Length is less then the actual block length
recorded on the tape even if the SILI bit is set to
one. The Error Code will be set to N
O ADDITIONAL SENSE
INFORMATION
,
ILLEGAL LENGTH BLOCK READ
. The illegal length
indicator (ILI) and Valid (VADD) bits in the sense
data list will be set to one. The Information Bytes
will be set to the requested Transfer Length minus
the actual block length (a negative number). This
means that the absolute value of the Information
Bytes indicates the number of byte not transferred
from the block read. When the command has terminated,
the logical tape position will be located after the
incorrect length block (end of partition side).
Variable Block Mode
When the Block Size field in the Block Descriptor
List of the MODE SELECT command is set to zero
(Variable Block mode), a SILI bit of one indicates
that the Drive will not return CHECK CONDITION status
if the only error is that the Transfer Length does
not match the actual block length recorded on the
tape. When the command has terminated, the logical
tape position will be located after the incorrect
length block (end of partition side).
17.3.4.2. FIX Bit Set to ONE
If the actual block length (length of block found on the
tape) is smaller than the configured Block Size (see
MODE SELECT command), only the actual block length is
transferred. If the actual block length is larger than
the configured Block Size, only the configured Block
Size is transferred.
The READ command will then be terminated with CHECK
CONDITION status. The Error Code will be set to N
O
ADDITIONAL SENSE INFORMATION
,
ILLEGAL LENGTH BLOCK READ
. The
illegal length indicator (ILI) and Valid (VADD) bits in
the sense data list will be set to one. The Information
Bytes will be set to the requested Transfer Length minus
the actual number of blocks transferred (not including
the incorrect length block). The block with the
unexpected length is not counted among the transferred
blocks. When the command has terminated, the logical
tape position will be located after the incorrect length
block (end of partition side).
17.3.4.3. Illegal Length Summary
The table shown below summarizes the illegal length
handling. The Illegal Length Type column shows
Underlength when the Transfer Length is larger than the
actual block length. The Illegal Length Type column
shown Overlength when the Transfer Length is less than
the actual block length.
