System Tables Views Oracle PLSQL

SQL>
SQL> set echo on;
SQL>
SQL> create table t1 ( x int );
Table created.
SQL> create table t2 ( x int );
Table created.
SQL>
SQL> insert into t1 values ( 1 );
1 row created.
SQL> insert into t2 values ( 1 );
1 row created.
SQL>
SQL> select username, v$lock.sid, id1, id2, lmode, request, block, v$lock.type
  2  from v$lock, v$session
  3  where v$lock.sid = v$session.sid and v$session.username = USER
  4  /
USERNAME                              SID        ID1        ID2      LMODE    REQUEST      BLOCK TY
------------------------------ ---------- ---------- ---------- ---------- ---------- ---------- --
RNTSOFT                                 23      16651          1          3          0          0 TO
RNTSOFT                                 23       8655          1          3          0          0 TO
RNTSOFT                                 23      16944          1          3          0          0 TO
RNTSOFT                                 24          0         22          6          0          0 JQ
RNTSOFT                                 38          0         21          6          0          0 JQ
RNTSOFT                                 23      16999          0          3          0          0 TM
RNTSOFT                                 23      17000          0          3          0          0 TM
RNTSOFT                                 23     655364        647          6          0          0 TX
8 rows selected.