How to enable trace for a Session?

Use the below steps to trace the Sessions.

Step 1: Login as sysdba
$sqlplus “/as sysdba”
Step 2: Execute the below query to get sid and serial#
SQL> select sid, serial# FROM v$session where username = 'USER_NAME';
Step 3: Enable trace Session using the below
SQL>exec dbms_system.set_sql_trace_in_session(sid,serial#,TRUE)
e.g: SQL> exec dbms_system.set_sql_trace_in_session(100,2018,TRUE)
Step 4: Check the trace files from user_dump directory.
SQL> select value from v$parameter where name = 'user_dump_dest';
Step 5: Check the trace (.trc) files from user_dump_dest directory.
Step 6: Disable trace session using the below
SQL>exec dbms_system.set_sql_trace_in_session(sid,serial#,FALSE)
e.g: SQL> exec dbms_system.set_sql_trace_in_session(100,2018,FALSE)