Can anyone say when Oracle is justified? I have yet to encounter a problem the postgres or mysql didn't support but alas I have not worked on everything.
Consistency. Your enterprise depends on terabytes of hyper valuable information (Wallmart with their sales data), can you guarantee that you won't end up with corruption issues? Or that the next version will work with your system too?
That said as long as you make less than 20 mil/year, Oracle isn't likely to be the best solution.
Just a quick question: which engine do you use for your MySQL system?
When the ERP application you are installing has in it's specs
- Supported database: Oracle
I am sure a crack Postgres guy can bash and file that sucker to work. But the vendor will not support the result, and some places, some situations, that really counts for a great deal.
Oracle isn't selling databases. They're selling database support. Similar to how IBM operates - they make good stuff, but you're really not paying for the hardware. If you were, they'd be outrageously expensive compared to something built more simply - see Backblaze, for an example: http://blog.backblaze.com/2009/09/01/petabytes-on-a-budget-h... .
(I too wonder what technical marvels it can perform which justify the cost).
But occasionally you gotta spend money to make money.