Re: How are INDEXES BALANCED?

Kevin Loney <kevin.loney_at_astramerck.com> wrote in article <01bcbf88$4315f060$aa9e02a7_at_LONEYK.astramerck.com>...
>
> > > I need to know if an index is not balanced, how do I get it balanced
 or
 is
> > > it done automatically? For example, when I enter an order number to
 an
> > > order entry system and the numbers are sequentially numbered, are the
> > > records added to the b-tree in one straight line to the tree?
> > >
> > The short answer is that Oracle automatically balances an index (or so
 I've
> > been told). The logic for doing so is straightforward enough that, if
 they
> > didn't, you'd have to go over and slap Larry Ellison upside the head.
> >
>
> Then get slapping. Oracle does not automatically rebalance its indexes.
> If it
> did, then the performance of your inserts would be unpredictable. The
 only
> way to rebalance an index is to drop and recreate it, or use the alter
> index
> rebuild option in 7.3.
>
> Kevin Loney.

Hm. I was told that it did by one of the Oracle instructors - Al Williamson (Oracle Canada) - who has a pretty impressive history, with Oracle and otherwise. And your source is ?

Anyway, who says the performance of inserts *is* predictable? By definition any multiuser software cannot perform deterministically anyway, so why would they leave off automatic balancing for that? And rebalancing involves perhaps a half-dozen writes extra on every x/2 record additions (on a *big* file), where x is the number of branches in an index record (This formula is not authoritative - more off the cuff based on my own personal experience - so don't drag out the textbooks).

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