*trace-print-circle* controls how circular structures are printed during output from tracing. It allows the printing of circular structures by the tracer to be controlled independently of the usual printing mechanism, which is governed by
*print-circle* is bound to the value of
*trace-print-circle* while printing tracing information.
USER 19 > (setq *trace-print-circle* t)
LispWorks User Guide and Reference Manual - 13 Feb 2015