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M-Pact combines two powerful tools,
CMPRS and PACK, to create a complete disk storage and
compression package.
PACK
PACK addresses one of the major problems of today's
computer installations, disk storage. With the ever-increasing
demands to keep more and more data on-line, computer
installations are faced with the need to continually
install more disk storage devices with even greater storage
density and capacity. This situation leads to the inevitable
problems of the cost of more disk drives, floor space
for the new disk drives and controllers, air-conditioning
upgrades, and the scheduling of long running backup jobs
with their ever increasing number of magnetic tape reels.
If you use VSAM and are not using PACK you are probably
wasting valuable disk space. Many installations have
files that contain records where a only a small amount
of the record is used, giving rise to large areas of
unused space, and records not being efficiently blocked
into VSAM Control Intervals and accordingly Control Areas.
PACK addresses these problems for Entry- and Key-Sequenced
VSAM files by allowing the user to compress the data
on selected files, and thus reduce the amount of space
required to hold such files.
The amount, which can be saved by compression, depends
on the contents and layout of the user's records, and
the degree of compression chosen by the user. PACK’s
sophisticated algorithms have achieved compression of
more than 70%.
PACK includes a file analysis program, which can be
run against selected files to establish the potential
compression ratio, and thus the value of using PACK for
the file, and the site generally.
PACK is fully transparent to programmers, operators,
and application programs. Selected files are re-DEFINED
and reloaded, after which the compression process is
automatic and invisible.
CMPRS
CMPRS is a program product used to compress 3270 CRT
or printer output data transmission. This reduces response
time and reduces contention among terminals on the same
line. CMPRS functions by removing repetitive characters
from the data stream and rebuilding the screen (or printer)
buffer so that the 3270 will construct the intended image
at the terminal. An optional feature, called "inbound
compression" may be used to further reduce transmission
by suppressing characters known to already be on a CRT
screen. Transmission reduction typically varies between
15 and 75 percent, depending on application programs
and data entered by terminal operators. Response time
improvement depends on the reduction amount and the line
speed.
CMPRS is supplied with a CRT transaction, which is used
to display statistics on the compression effectiveness.
The transaction displays terminal I/O counts, character
totals before and after compression, and calculates compression
percentage, for all local terminals collectively, all
remote terminals, and for each individual terminal. CMPRS
supports all telecommunication protocols (BTAM, TCAM,
VTAM), under z/OS.
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