HP A3716A DDS-3 Autoloader User's Manual - 3716-96001

Glossary-3
LZ
Lempel-Ziv. A family of compression algorithms, all of which remove
redundancy from data by encoding the data through a dictionary that is
implicit in the compressed data.
magazine
A holder for up to six tape cartridges used in HP autoloaders.
Media Recognition
System
A method by which a drive can recognize data-grade cartridges. The tape
has a series of stripes on its transparent leader tape that the drive can
identify.
By default, the drive will treat a non-Media Recognition System cartridge as
write-protected, and will not write data to it. However, it is possible to
switch the recognition system off using the configuration switches on the
underside of the autoloader.
offline
The autoloader is offline if the cartridge is currently unloaded or not in the
drive. The host has limited access, and cannot perform any commands that
would cause tape motion. However, the host can load a cartridge if one is
inserted, and can execute any diagnostic tests that do not require tape
motion.
online
The autoloader is online when a cartridge is loaded. The host has access to
all command operations, including those that access the tape, set
configurations and run diagnostic tests.
partition
A part of a tape that can be treated as a complete and independent whole.
A tape can have one or two partitions, of a size determined by the host.
QIC
Quarter-Inch Cartridge. An industry committee for standardization of
quarter-inch cartridge formats.
random mode
In random mode, cartridges are used in the order dictated by the host
(through SCSI) or the user (through the front panel buttons), rather than
sequentially, as in stacker mode. For each cartridge to be used, the host
must issue a SCSI MOVE MEDIUM command to instruct the autoloader to
move the cartridge from the magazine to the drive. When the cartridge is
full, or when no further use is to be made of it, the host must again use the
MOVE MEDIUM command to load another.
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. The audio DAT two-head drum is replaced by a four-head drum for
this, with two read-only heads, and two write-only heads. Frames are only
rewritten when necessary, so speed and capacity are affected minimally.
redundancy
Repetition within data, where a string of characters occurs with greater
frequency than the norm. By replacing the string with a single symbol, the
data can be compressed without losing any information.