Using SQL Plus Autotrace on Oracle Database

SQL*Plus offers an AUTOTRACE facility that will display the query plan and execution statistics as each query executes. Example: 

SQL> SET AUTOTRACE ON
SQL> select * from dept where deptno = 40;

    DEPTNO DNAME          LOC
---------- -------------- -------------
        40 OPERATIONS     BOSTON

Execution Plan
----------------------------------------------------------
Plan hash value: 2852011669

---------------------------------------------------------------------------------------
| Id  | Operation                   | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |         |     1 |    20 |     1   (0)| 00:00:01 |
|   1 |  TABLE ACCESS BY INDEX ROWID| DEPT    |     1 |    20 |     1   (0)| 00:00:01 |
|*  2 |   INDEX UNIQUE SCAN         | PK_DEPT |     1 |       |     0   (0)| 00:00:01 |
---------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - access("DEPTNO"=40)

Statistics
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          2  consistent gets
          0  physical reads
          0  redo size
        443  bytes sent via SQL*Net to client
        374  bytes received via SQL*Net from client
          1  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed

Find Oracle session ID using OS pid

SELECT 
a.sid,
b.spid
FROM v$session a, v$process b
WHERE a.paddr = b.addr
and b.spid = 1234;