A true open-source relational database.
Firebird scales impressively, from an embedded, single-user model to enterprise-wide deployments with multiple 2Tb+Gb databases running with hundreds of simultaneous clients. Firebird supports a number of hardware and software platforms: Windows, Linux, MacOS, HP-UX, AIX, Solaris and more. It runs on at x386, x64 and PowerPC, Sparc and other hardware platforms, and supports an easy migration mechanism between these platforms.
Firebird is included into the following Linux repositories: Fedora, OpenSuse, CentOS, Mandriva, Ubuntu. One of the key Firebird features is its multi-generational architecture, which enables the development and support of hybrid OLTP and OLAP applications. This makes a Firebird database capable of serving simultaneously as both an analytical and an operational data store, because readers do not block writers when accessing the same data under most conditions.
Firebird supports stored procedures and triggers, and has comprehensive SQL92 support.