• Subject: Re: PF File Definition questions...
  • From: nina jones <ddi@xxxxxxxxxxxxxxxxx>
  • Date: Thu, 14 Oct 1999 22:49:05 -0500
  • Organization: Data Design Inc. http://www.datadesigninc.com

> Was wondering how folks define PF's when it comes to keyed or not.

> Is there something I'm missing when it comes to NOT having the "most
> common" field(s) in a PF defined in the PF a key field(s) ?

> Then handle the less obvious stuff in LF's ?

well, that's what i've always done, but it may be old habits.  i've seen
some debates on that in the past, and can't remember what the
conclusions were..  

> Why PF's with NO key fields ?

we've had a few we've done that way, when there's no clear index.  but
normally we make the unique key the index defined with the pf, and use
the lf's for alternate views.

> Also, I was told YEARS ago (on the S/38) that you should try to keep the
> number of LF's over a PF to a minimum, say 3, 4 tops and let your
> program handle the level breaks, etc. to help system performance. Even
> on the AS/400 there has GOT to be some truth to that just due to the
> fact that there aren't a BUNCH of access paths that have to be rebuilt.
> I've seen some vendor packages with a hundred LF's over one PF !!!!

i would tend to agree.  also reorgs take longer!  we have a major file
in our software that has 5 indexes, and can take up to an hour to
rebuild them, based on the cpu and the size of the file.  also, when you
make maintenance changes to the file, all those indexes have to be
maintained.  

nj
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