David H. Lipman wrote On 07/26/06 20:01,:

   Well, that would be one of those areas where I *really*
don't speak for Sun ...

... but I'll speculate, with the understanding that this is
*only* speculation and *not* any kind of Official Say-So.
(If people think I'm being overcautious with the disclaimers,
just look at the nature of David's follow-up question and
how quickly it was fired off.)

   If I'm trying to maintain a production system, upgrades
and patches and stuff are a big source of worry.  I may have
great faith that Sun and IBM and BEA and Oracle have all
tested their products and their product upgrades with care,
but I'm also aware that they probably haven't tested the
exact combination of components from all four that I happen
to be using.  And then there are the home-grown applications
my own shop's programmers have turned out ...  What's going
to happen when I discover that upgrading both the Sun piece
and the BEA piece causes the Oracle piece to run just a wee
bit faster, thus exposing an unsuspected race condition in
the home-grown app that books all our sales?

   Unforeseen version interactions are a fact of life, an
unfortunate fact but a fact nonetheless.  So I test all the
new stuff as best I can on a non-production machine, and then
I cross my fingers, hold my breath, and apply the upgrade to
my production system -- and one thing I've made *really* sure
of is that I have a quick and reliable way to return to the
status quo ante if anything goes wrong.

   I would be *really* *not* *pleased* if the upgrade were
to wipe out the old version automatically!  It may only happen
once in a hundred times that I need to do an emergency roll-
back in the middle of the night, but on that hundredth time I
*really* need to be able to do it just as smoothly and quickly
as I can.  I do *not* want to go back to some vendor's web site
and start hunting for downloads of obsoleted versions and then
hoping I can recall how I answered the installation script's
questions; I want the old stuff still sitting on the system,
unaltered and ready to roll as soon as I change an environment
variable or re-target a symlink or flip a registry key or
whatever.

   Not everyone has (or needs) quite such a mind set; some
people are perfectly happy to just click "Do to me whatever
you like" on a vendor's product maintenance page, and watch
the pretty lights while the new stuff installs automagically.
(My impression is that these are the same people who have
never heard of backups.)  If I were designing Java's upgrade
procedures -- which I'm not; this is all speculation, right? --
I would consider it more important to allow a careful person
to do his job carefully than to make it easy for a carefree
person to be careless.

   In an ideal world, system maintenance would be easy --
heck, in an ideal world it would be unnecessary!  But even
though maintenance is harder than it might be, given the
current state of technology I don't think it's an awful lot
harder than it must be.