The OS page size is what determines how much is read into memory on each
disk read. So if your page size is 2k (not unusual) then only the first
2k of your dictionary is going to be read in the first disk read
regardless of your modulo. This is generally why your group size and OS
page size should be the same (yes, I know...unless you have some kind of
giant records, or dynamic files, or any of the other "YaBut's").
jjuser ud2 wrote:
So...this school of thought says that modulo 1 is a good thing, and
that it forces files into memory. The question is -- is the school of
thought speculation, or is it true?
On 10/16/06, Ray Wurlod <[EMAIL PROTECTED]> wrote:
Interestingly, at least in some flavors, you can do something similar
with file dictionaries. In IDEAL flavor you can move I-descriptors
to some other file, and reference them via "R" (remote) types. I
can't find it documented, but it did work when I tried it.
I-descriptors are 20+ fields long (maybe many more) and can be quite
large, especially if the expression is large. The same
considerations apply when searching for a dictionary item from a
query as for a VOC item. How many of you bother to tune your file
dictionaries? (There is another school of thought that says leaving
them with modulo 1 forces the entire dictionary to be read into
memory, leading to more efficient location of subsequent items. But
if that were really the case, don't you think the default size of the
VOC file would be modulo 1 also?)
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Jeff Schasny
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