TYPO3 CMS relies on storing its data in a Relational database management system (RDBMS). It works out of the box with MySQL. It is known to work fine with MySQL forks like MariaDB, although they are not officially supported.

The \TYPO3\CMS\Core\Database\DatabaseConnection functions as a database abstraction layer, handling all calls to the database. It can be overridden to work with another RDBMS. The “dbal” system extension does just this, providing support for Microsoft SQL Server, Oracle and PostgreSQL. It may work with other RDBMS, but without official support.

Activating “dbal” does cause a performance penalty, due to query interpretation and table mapping overhead.