Search notes:

Oracle: Init parameter SQL_TRACE

alter session set sql_trace=true;

select value from v$diag_info where name = 'Default Trace File';

… execute some SQL statements…

alter session set sql_trace=false;

See also

dbms_monitor.session_trace_enable and session_trace_disable.
Trace files
Prerequisites for filling V$SQL_PLAN_STATISTICS and V$SQL_PLAN_STATISTICS_ALL
The parameter tracefile_identifier 
alter session set events '10046 level …';
init parameters

Index