PL/SQL Packages DBMS_TRACE

Trace PL/SQL functions, procedures, and exceptions.

Subprocedures:

SET_PLSQL_TRACE     Start tracing in the current session. 

CLEAR_PLSQL_TRACE   Stop trace data dumping in session. 

PLSQL_TRACE_VERSION Get the version number of the trace package.  

For full documentation of the packaged procedures above see the Oracle Manual:
"Oracle9i Supplied PL/SQL Packages and Types Reference"

or the book Oracle Built in Packages by Steven Feuerstein et al