User's Manual

Data compression
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Data Compression
Introduction
Overview
Typical data streams of text, graphics, software code or other forms of data contain
repeated information of some sort, whether it is at the text level where you can
readily recognize regular repetitions of a single word or at the binary level where the
repetitions are in bits or bytes. Although most data is unique and random, the binary
level data exhibits patterns of various sizes that repeat with varying degrees of
regularity.
Storage efficiency is increased if the redundancies or repetitions in the data are
removed before the data is recorded to tape. Data compression technology functions
to significantly reduce or eliminate the redundancies in data before recording the
information to tape. The compression increases the amount of data that can be
stored on a finite medium and increases the overall storage efficiency of the system.
With data compression, the redundant information in a data stream is identified and
then represented by codewords or symbols, which allow the same data to be
recorded in a fewer number of bits. These symbols or codewords point back to the
original data string, using fewer characters to represent the strings. Because these
smaller symbols are substituted for the longer strings of data, more data can be
stored in the same physical space.
Some important benefits result from data compression in DAT drives:
•
The same amount of information can be stored on a smaller length of tape.
•
Increased data density on a given length of tape.
•
Performance can more closely parallel to that of high-transfer-rate computers.
•
More information can be transferred in the same time interval.
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