One of the most important responsibilities of an Oracle Database Administrator or Performance Analyst, when it comes to performance diagnostics, is to determine how users access the database. This article is an attempt to show the different ways one can activate tracing of an Oracle session for performance diagnostics. While the Oracle documentation mentions some of the methods, it doesn't cover them all. This article consolidates many methods of tracing an Oracle session, some of which are well documented, as well as methods that are undocumented and reserved.