Actions enable your DTrace programs to interact with the system outside of DTrace.
The most common actions record data to a DTrace buffer. Other actions are
available, such as stopping the current process, raising a specific signal on the
current process, or ceasing tracing altogether. Some of these actions are destructive in
that they change the system, albeit in a well-defined way. These actions may
only be used if destructive actions have been explicitly enabled. By default, data
recording actions record data to the principal buffer. For more details on the principal buffer
and buffer policies, see Chapter 11, Buffers and Buffering.