Oracle PL/SQL Tutorial/System Tables Data Dictionary/dba locks

Check for locks held after starting the transaction

SQL>
SQL> CREATE TABLE emp (
  2    id         NUMBER PRIMARY KEY,
  3    fname VARCHAR2(50),
  4    lname  VARCHAR2(50)
  5  );
Table created.
SQL>
SQL> INSERT INTO emp (id, fname, lname)VALUES (1, "A", "B");
1 row created.
SQL> INSERT INTO emp (id, fname, lname)VALUES (2, "C", "D");
1 row created.
SQL> INSERT INTO emp (id, fname, lname)VALUES (3, "E", "F");
1 row created.
SQL> INSERT INTO emp (id, fname, lname)VALUES (4, "G", "H");
1 row created.
SQL> INSERT INTO emp (id, fname, lname)VALUES (5, "G", "Z");
1 row created.
SQL>
SQL> UPDATE emp
  2  SET fname = "Ronald"
  3  WHERE id = 44;
0 rows updated.
SQL>
SQL>
SQL> SELECT d.session_id sid, d.lock_type, d.mode_requested,
  2         d.mode_held, d.blocking_others
  3  FROM dba_locks d, v$session v
  4  WHERE v.username = "PLSQL"
  5  AND d.session_id = v.sid;
no rows selected
SQL>
SQL>
SQL> drop table emp;
Table dropped.

Get the name and type of object locked

SQL>
SQL> CREATE TABLE emp (
  2    id         NUMBER PRIMARY KEY,
  3    fname VARCHAR2(50),
  4    lname  VARCHAR2(50)
  5  );
Table created.
SQL>
SQL>
SQL>
SQL> SELECT dbl.lock_type, dbl.mode_held, dbl.blocking_others,
  2         dbo.object_name object_locked, dbo.object_type
  3  FROM dba_locks dbl, v$session v, dba_objects dbo
  4  WHERE v.username = "PLSQL"
  5  AND dbl.session_id = v.sid
  6  AND dbo.object_id = dbl.lock_id1;
no rows selected
SQL>
SQL>
SQL> drop table emp;
Table dropped.
SQL>