Re: Why is the object size on SAVOBJ DTACPR(*HIGH) bigger than on DTACPR(*MEDIUM)?

Rob,

It's different depending on the compressibility of the objects.
*MEDIUM - TERSE algorithm. Medium compression is usually slower than
low compression but faster than high compression. The
compressed data is usually smaller than if low
compression is used and larger than if high
compression is used.

*HIGH - LZ1 algorithm. High compression is usually slower and the
compressed data is usually smaller than if low or
medium compression is used.

Note the "usually"...

Also found this is the infocenter.
"The IBM LZ1 algorithm tends to produce better compression on shorter
input strings than the simple TERSE algorithm. "


HTH,
Charles


On Tue, May 3, 2011 at 3:03 PM, <rob@xxxxxxxxx> wrote:

I redid some time trials for DTACPR on SAVOBJ.  I took a 26GB data file
and saved it to a save file.  Timed it and checked the size of the save
file upon completion.

Object                Size    Time
datafile        26,811,564,032
*NO         29,963,624,448   06:17
*MEDIUM      4,843,528,192   15:44
*HIGH        4,844,969,984   28:57
Why use *HIGH if it makes a bigger save file (freshly created) and takes
significantly longer than *MEDIUM?  No, I didn't do anything different
like save access paths on one and not the other.  The data only gets
updated once a week and today is not the day.  Does anyone at IBM check
these?  Is it different for different objects, like journal receivers or
management collections, versus files?

SAVOBJ OBJ(IFSLIST) LIB(ROUTINES) DEV(*SAVF) OBJTYPE(*FILE) SAVF(ROB/ROB)
 DTACPR(*HIGH  )

7.1
WRKPTFGRP PTFGRP(*ALL) PTFGRPLVL(*INSTALLED)
PTF Group             Level
SF99710               10229
SF99709                  27
SF99708                   4
SF99707                   1
SF99701                   6
SF99637                   2
SF99627                   2
SF99617                   5
SF99572                   5
SF99369                   4
SF99368                   5
SF99367                   2
SF99366                   2
SF99364                   3
SF99363                   4
SF99362                   9
SF99145                   1



Rob Berendt
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