Of course you can switch databases, but in practice it is extremely expensive. That's a big reason why it is pretty rare. Why use a closed source tool and take on that risk when great open source ones exist?
For a lot of companies, switching databases is effectively impossible. Perhaps not quite as impossible as switching game engines, but certainly impossible enough that it would kill the business. A lot of companies use database specific functionality that's far from trivial to replicate in another database. A lot of that database specific functionality can also be legacy that no one really understands anymore. Migrating without an option to keep these poorly understood but critical systems will set you up for unexpected data loss, corruption or availability issues. And that's after spending a year on your migration. If Oracle pulls anything like Unity here, this will kill off a lot of companies
>Why use a closed source tool and take on that risk when great open source ones exist?
in the case of servers: because open source servers literally can't support your scale of business. That's one of the few places where Open Source can never truly succeed: when you need a lot of hardware and the operating costs exceed any income coming in.
By that point it is a lot better to roll your own servers. But that is of course crazy expensive. Even other multibillion dollar corporations choose to leave some server management to places like Amazon/Microsoft.
