Just a quick note that SQL_TRACE parameter is no longer valid – it is deprecated as of Oracle 10g Release 2 in favor of DBMS_MONITOR subprograms. I realized that after start up warning:
SQL> startup ORA-32004: obsolete or deprecated parameter(s) specified for RDBMS instance ORACLE instance started.
Though SQL_TRACE is still working in 11.2.0.1, it’s a good idea to start forgetting about it.
Timur Akhmadeev's blog 