-If 'SESSION' is omitted, the LTTng tracers are started for the current
-tracing session (see linklttng:lttng-create(1) for more information
-about the current tracing session). Otherwise, they are started for the
-existing tracing session named 'SESSION'. `lttng list`
-outputs all the existing tracing sessions (see linklttng:lttng-list(1)).
+The selected tracing session must be inactive (stopped). A tracing
+session is inactive on creation (see man:lttng-create(1)).
+
+An active tracing session is an implicit recording event rule condition
+(see man:lttng-enable-event(1)). In other words, a recording event rule
+cannot match an event when its tracing session is inactive.
+
+A `start-session` trigger action can also start a tracing session
+(see man:lttng-add-trigger(1)).
+
+Stop an active tracing session with the man:lttng-stop(1) command.