Open-source DBMSs like MySQL, MariaDB and PostgreSQL have gained recognition in professional circles for their speed and robustness. They first won acceptance in small and medium businesses, but have since moved into larger companies. At the other end of the entrepreneurial spectrum, in the biggest corporations, DB2 has quietly remained ubiquitous. Orsys is not affiliated with any software publisher and has developed a series of courses around these less well-known DBMSs, from getting started to tuning.