Oracle

Does the wiki support Oracle databases for storing wiki content?

Offers various database editions. The enterprise version is not free (far from it), thus many open source web applications (most wikis) are not built to support it. It's not just the price tag which is heavyweight. It takes a fair bit of specialist knowledge to get to grips with oracle database administration, and it takes fair chunk of your CPU and disk space to run it, so this is not an option for the casual hobbyist.

Luckily Oracle also has a free to use and distribute version of their database that will be well suited as back-end for a Wiki. For more details, see Oracle XE.

If you want to run your wiki on oracle (perhaps you already have an Oracle database), then this will narrow your options considerably. Pay close attention to what is said about oracle support for that wiki.

You might prefer to consider the option of installing MySQL or SQLite just for your wiki. Or look for a wiki which uses Text Files for storage. This will widen your options.