The lock for "select ... for update"

Question

1. select * from tbl for update;
2. SELECT p.spid, a.serial#, c.object_name, b.session_id, b.oracle_username, b.os_user_name FROM v$process p, v$session a, v$locked_object b, all_objects c WHERE p.addr = a.paddr AND a.process = b.process AND c.object_id = b.object_id
Why there is two records with the same session_id:
1 14728 11961 TBL 290 STAR bil
2 14732 50904 TBL 290 STAR bil
The SQL "select ... for update" will generate two locks?

Answer 1

I get one lock:
SQL> SELECT p.spid, a.serial#, c.object_name, b.session_id, b.oracle_username, b.os_user_name FROM v
$process p, v$session a, v$locked_object b, all_objects c WHERE p.addr = a.paddr AND a.process = b.p
rocess AND c.object_id = b.object_id;
no rows selected
SQL> select * from emp for update;
     EMPNO ENAME      JOB              MGR HIREDATE                   SAL       COMM     DEPTNO
      7369 SMITH      CLERK           7902 17-12-1980 00:00:00        800                    20
      7499 ALLEN      SALESMAN        7698 20-02-1981 00:00:00       1600        300         30
      7521 WARD       SALESMAN        7698 22-02-1981 00:00:00       1250        500         30
      7566 JONES      MANAGER         7839 02-04-1981 00:00:00       2975                    20
      7654 MARTIN     SALESMAN        7698 28-09-1981 00:00:00       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-05-1981 00:00:00       2850                    30
      7782 CLARK      MANAGER         7839 09-06-1981 00:00:00       2450                    10
      7788 SCOTT      ANALYST         7566 09-12-1982 00:00:00       3000                    20
      7839 KING       PRESIDENT            17-11-1981 00:00:00       5000                    10
      7844 TURNER     SALESMAN        7698 08-09-1981 00:00:00       1500          0         30
      7876 ADAMS      CLERK           7788 12-01-1983 00:00:00       1100                    20
      7900 JAMES      CLERK           7698 03-12-1981 00:00:00        950                    30
      7902 FORD       ANALYST         7566 03-12-1981 00:00:00       3000                    20
      7934 MILLER     CLERK           7782 23-01-1982 00:00:00       1300                    10
14 rows selected.
SQL> SELECT p.spid, a.serial#, c.object_name, b.session_id, b.oracle_username, b.os_user_name FROM v
$process p, v$session a, v$locked_object b, all_objects c WHERE p.addr = a.paddr AND a.process = b.p
rocess AND c.object_id = b.object_id;
SPID            SERIAL# OBJECT_NAME                    SESSION_ID ORACLE_USERNAME                OS_USER_NAME
2536                  4 EMP                                    25 HOEK                           hoek
1 row selected.What database version are you using?
(the result of: select * from v$version; )