Re: 30 instances on one host

In article <db479d88.0206190454.37bcc26f_at_posting.google.com>, you said (and I quote):
> I'm not a DBA, so can somebody explain what is wrong with having many
> instances on a machine? What are the performance, robustness and
> scalability issues?

Posible redundant waste of common resources. A LOT of them.

>
> What would you recommend is the maximum number of instances per
> machine that you'd want (I realise this depends on machine spec).

Development, I couldn't care less (within reason!). Production? Two, and that's it. And I don't care how big the system is.

> One (development and testing) has at least 17 instances on it
> (assuming my tnsnames.ora is accurate, which it probably is)

Shouldn't be a problem, although IMHO it's way too high.

>
> Our two production machines have 6 and 8 instances respectively.
>

Way over the top.

> I take it that this is not ideal ;-)

Anything in my reply that hints at that? ;-)

>
> Now I know that management are a bit tight when it comes to cash, so
> it may be that they're saying we can't have any more machines. So
> what do you do in this case?

Explain to management that it is a false economy.

> Each application has its own database.

That is truly deranged. There is no valid argument that can be sustained nowadays to defend such a strategy.

> Is it better to consolidate applications into the same database?

Yes, of course.

> Surely this isn't very good if you database crashes.

As Oracle is currently, your Unix box is more likely to crash than the database. Are they willing to buy one box for each application?

There are now many mechanisms available to ensure that the database software will not be the cause of undue downtime.

-- 
Cheers
Nuno Souto
nsouto_at_optushome.com.au.nospam