You can read about someone else's
problems with it as well here:

http://christianbilien.wordpress.com/2007/03/

post of March 14th (just in case I get the usual
interjection insinuating "somehow I'm the only one
with this problem"...)

The Metalink note mentioned there talks about it.
The bug mentioned in someone else's post
also explains what the problem is.

I personally opened two calls with Oracle nearly
three years ago with precisely the same problem,
first with 9i, then with 10g.  Which were closed by
Oracle Support as "known problem, fixed in 11g".

Boy, did this cause us a problem!...
Try to explain to google for example that 3.5
million of their clicks just didn't get accounted
for because they got aggregated into another
table.  They don't like that sort of explanation...

3(three) years ago!  And it was a "known" bug
waaaaaay back then...
In fact, it's been "known" since the auto-sga
started, in 9i early releases.

It is absolutely ludicrous it hasn't yet been fixed
in ALL available releases.  Not just 11g
(*IF* it is fixed there...).

And then some folks have the gall to call
me cynical when I point out that this is
inadmissible in a product that:

1- is charged for, not freeware
2- that claims to be "enterprise class"
3- that claims to be "unbreakable"
4- that is pushed as multi-schema,
multi-aplication capable.

As a matter of additional info and to end in
a positive note: read the whole of Christian's
blog, it is well worth someone's time no matter
how much they know about Oracle.

Kevin Closson mentioned it a while
ago and I thank God he did!