"Marshall Spight" <mspight@dnai.com> wrote in message
news:mhMlb.2417$9E1.18525@attbi_s52...
> "Bob Badour" <bbadour@golden.net> wrote in message
news:W46dnf4tbfF1DwiiU-KYgw@golden.net...
> >
> > All physical structures will bias performance for some operations and
> > against others.
>
> This strikes me as a succinct statement of the value of
> data independence. One has the option (but not the
> requirement) to adjust the physical structures the DBMS
> uses while keeping the logical model (and therefor all
> application code and queries, etc.) unchanged.
>
> Unless one has data independence, one does not have
> this option; one will be locked into a particular
> performance model. This is why I found the MV
> guy's obvious pleasure at being able to precisely
> describe the performance model for his DB as odd:
> I thought it a deficit to be able to say what it was;
> he thought it an asset.
It becomes an obvious deficit as soon as he needs to improve upon the
performance for some operation and he has no way to do it. Thus, he lacks
the option to gain the factor of eight improvement for the first query
offered by clustering.
> Marshall
>
> PS. This is nothing you don't know, Bob; just a
> comment for the group.
Of course. Likewise.