Product manual

46 Viper 200 LTO Product Manual
attempt than the native (uncompressed) size, then the record is written in its native
form.
The intelligent data compression utilizes two compression schemes:
• Scheme-1 is a LZ1 based compression scheme using a history buffer to achieve
data compression.
• Scheme-2 is a pass-through compression scheme designed to pass
uncompressible data through with minimal expansion.
There are three specific requirements for compliance with the LTO specification.
• First: the output data stream must be decompressible following LTO rules to
create the input sequence of records and File Marks perfectly.
• Second: an LTO compressed data stream may not contain any of the eight
reserved Control Symbols.
• Third: while control symbols allow switching to Scheme 2, this should never be
used by operational software because this capability is only for diagnostic and
testing purposes.
Software data compression should never be used because the Viper's built-in
intelligent data compression is much more efficient than software data compression
systems.
The Viper 200 uses a derivative of ALDC-2 lossless data compression that includes
additional control codes for intelligent data compression.