Group size appears adequate (although anytime anything hashes into the group(s)
with the largest record [3267b], you'll split: 3267 is 79.8% of 4096, so if you
have a lot of records up in the 3K range, you may want to increase group size
and decrease min modulus accordingly), but the minimum modulus should be a
prime north of the current modulus, with a padding factor based on growth
expectations. The sweet spot is where you have enough data in each group to
avoid merging (I'd argue that 50% is a bit high for the merge; but that's
because I'm unafraid of unused space, while I'm averse to file maintenance
overhead), but not so much that you do a lot of splitting. You should do a
count on the number of records, too. It almost never makes sense to have the
modulus exceed the number of records by a substantial percentage.
So, you should increase minimum modulus to 83267 or higher, unless you double
the group size to 8K, in which case something around 50K as a modulus sounds
good. I'd take the merge down a little, to maybe 30% or even less, and maybe
knock the split up a bit - say, 90% - to cut down on the splitting.
> From: cjausti...@hotmail.com
> To: u2-users@listserver.u2ug.org
> Date: Mon, 2 Jul 2012 14:55:21 -0500
> Subject: [U2] RESIZE - dynamic files
>
>
> I was wondering if anyone had instructions on RESIZE with a dynamic file? For
> example I have a file called 'TEST_FILE'
> with the following:
>
> 01 ANALYZE.FILE TEST_FILE
> File name .................. TEST_FILE
> Pathname ................... TEST_FILE
> File type .................. DYNAMIC
> File style and revision .... 32BIT Revision 12
> Hashing Algorithm .......... GENERAL
> No. of groups (modulus) .... 83261 current ( minimum 31 )
> Large record size .......... 3267 bytes
> Group size ................. 4096 bytes
> Load factors ............... 80% (split), 50% (merge) and 80% (actual)
> Total size ................. 450613248 bytes
>
> How
> do you calculate what the modulus and separation should be? I can't use
> HASH.HELP on a type 30 file to see the recommended settings
> so I was wondering how best you figure out the file RESIZE.
>
> Thanks,
>
> Chris
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