Sony SDX-900V Product Specifications page 202

15. Appendix H
Group: A fixed capacity set of frames written onto or read from the tape. A group contains one index and can contain
several records, partial records, File-marks and Set-marks.
Hard Error: A Hard Error is an un-correctable data error. During writing, this is defined as being uncorrected after
the RAW retry limit has been exceeded. During reading, a hard error is logged if a group is un-correctable.
Head Clog: Particles from the tape or from outside the drive adhere to the head gap on a read or write head and
obstruct the reading or writing of data. The particles will become dislodged by the operation of the internal head
cleaner and/or cleaning tape.
Index: Information stored at the end of a group which specifies the contents of the group. Every group except the
Vendor Group contains an index.
Lead-in Area: The first clause of the tape used for loading, BOT positioning, and tape usage logging.
Load: To insert a cassette into the drive. The drive automatically threads the tape and goes online.
LUN: Logical Unit Number, by which a device is identified on the SCSI bus. The Sony SDX-900V has an LUN of 0
fixed in the firmware.
MIC: Memory In Cassette.
Noise: Any kind of magnetic or electric interference detected by the electronics.
Off-line: The Sony SDX-900V is off-line if the tape is currently unloaded or not in the drive. The host has limited
access, and cannot perform any commands which would cause tape motion. The host can, however, load a tape, if
one is inserted, and can execute any diagnostic tests which do not require tape motion.
On-line: The Sony SDX-900V is online when a tape is loaded. The host has access to all command operations,
including those which access the tape, set configurations and run diagnostic tests.
Over Length: The incorrect length condition that exists after executing a read command when the length of the
actual block read exceeds the requested transfer length in the command descriptor block. Only the requested
amount of data is returned to the host.
Partition: The entire usable region of recording and reading paths in a volume or in a portion of a volume. If there is
more than one partition, they shall be numbered starting with ZERO (i.e., beginning of partition ZERO).
RAW: See Read-After-Write
Read-After-Write (RAW): Improves data integrity by reading data immediately after it is written and writing the
frame again if an error is found. Frames are only re-written as necessary, so speed and capacity are affected
minimally.
Repeat (N-group writing): Sometimes called multiple group writing, Repeat (N-group writing) repeats each group
of data so that there are N consecutive copies of each group on the tape. This is a simple way of improving data
integrity, but speed and capacity are sacrificed in writing all data several times.
Reserved: Reserved for future definition and detailing and not generally available for use. Reserved bits and fields
should be set to ZERO.
Set-mark: A mark written by the host to allow fast searching to a point on the tape without having to know the
number of records or file-marks that precede this point. A special recorded element within a partition, containing no
user data, which provides a segmentation scheme hierarchically superior to file-marks for use in addressing or fast
positioning on high capacity storage devices. (Also called Save-Set Mark)
SCSI (Small Computer System Interface): This computer device interface has been certified as an American
National Standard by ANSI. The standard contains the electrical specifications, communication protocol, and
command structure necessary to connect various computer peripherals to a host computer.
Soft Error: A soft error is a data error which can be corrected by a RAW rewrite during writing, or by C1, C2 or C3
ECC, or a read-retry during reading.
Spacing: The act of positioning the medium on a sequential access device.
System Area: A section in the Lead-in Area used to store the tape usage information.
15-2 SONY AIT-4 drive SDX-900V series Ver.2.1