When adding an SQL database as a datasource, the following error message might be printed when testing the connection:
Cannot connect to this database. Error message was: [JDBC driver class not found: oracle.jdbc.driver.OracleDriver]
This means that the appropriate JDBC driver, which is needed to connect to the database, is missing. You need to download it manually and add it to the folder WEB-INF/lib of your Confluence installation directory. After that restart Confluence. You can find a list of the JDBC drivers here.
For a detailed step-by-step tutorial, refer to our Getting Started Guide.