COMPRESSASM(8)              Legato NetWorker 4.0              COMPRESSASM(8)


NAME
       compressasm - NetWorker module for compressing and decompressing
       files

SYNOPSIS
       compressasm [ standard-asm-arguments ]

DESCRIPTION
       The compressasm is a standard, external ASM (Application Specific
       Module) used to compress files when they are saved and decompress
       files when they are recovered.

       See uasm(8) for a general description of ASM's and the [standard-asm-
       arguments].  It is intended that compressasm be invoked by uasm dur­
       ing save(8) or recover(8) operations.

       The compressasm uses a Legato implementation of Lempel-Ziv compres­
       sion coding to compress file pages (one page is always 8 Kbytes)
       while saving them.  This can result in less data being transmitted
       over the network and less data being stored.  Since the network and
       media subsystems are normally important performance bottlenecks, this
       can provide significant performance improvement, especially if the
       client processor is relatively fast.  Compression of 50-60% are typi­
       cal, but results vary with the content of the file.

       The per page compression technique will never cause data expansion.
       Since compression occurs on a per page basis, the efficiency of com­
       pressasm may be less than that of compress(1).

       Combining compressasm with a backup device that provides hardware
       compression will provide small, if any, improvement in tape utiliza­
       tion, since the algorithm used by compressasm is within a constant
       factor of optimal.

       Upon recovery, files are decompressed into their original form.

SEE ALSO
       compress(1), save(8), recover(8), uasm(8)



















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