Gets and sets the global tracing state..
tracing-enabled-p => enabledp
(setf tracing-enabled-p) enabledp => enabledp
A generalized boolean.
tracing-enabled-p determines whether tracing (by the Common Lisp macro trace) is currently on. This is independent of whether any functions are currently traced.
(setf tracing-enabled-p) switches tracing on or off according to the value of enabledp. This does not affect the list of functions that are currently traced.
LispWorks User Guide and Reference Manual - 13 Feb 2015