In Oracle® Clusterware Administration and Deployment Guide 11g Release 2 (11.2), the section, Troubleshooting and Diagnostic Output for CVU, says that:
You can enable tracing by setting the environment variable SRVM_TRACE to true. For example, in tcsh an entry such as setenv SRVM_TRACE true enables tracing. The CVU trace files are created in the CV_HOME/cv/log directory. Oracle Database automatically rotates the log files and the most recently created log file has the name cvutrace.log.0. You should remove unwanted log files or archive them to reclaim disk place if needed. CVU does not generate trace files unless you enable tracing.
To choose the location in which CVU generates the trace files, set the CV_TRACELOC environment variable to the absolute path of the desired trace directory.