ddl_lock_timeout 与 ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired

Connected to Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 
Connected as [email protected]:1521/orcl

SQL> 
SQL> INSERT INTO TEST SELECT 1 FROM dual WHERE NOT EXISTS(SELECT * FROM TEST);
1 row inserted
SQL> COMMIT;
Commit complete
SQL> BEGIN
  2    DBMS_SCHEDULER.CREATE_JOB(JOB_NAME   => 'TEST_JOB',
  3                              JOB_TYPE   => 'PLSQL_BLOCK',
  4                              JOB_ACTION => 'declare
  5      v_date date := sysdate + 10 / 24 / 60 / 60;
  6    begin
  7      loop
  8        dbms_lock.sleep(1);
  9        update test set t1 = t1 + 1;
 10        exit when sysdate >= v_date;
 11      end loop;
 12        commit;
 13    end;',
 14                              START_DATE => SYSDATE,
 15                              ENABLED    => TRUE,
 16                              AUTO_DROP  => TRUE);
 17    DBMS_LOCK.SLEEP(5);
 18  END;
 19  /
PL/SQL procedure successfully completed
SQL> TRUNCATE TABLE TEST;
TRUNCATE TABLE TEST
ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired

SQL> 

SQL> show parameter ddl_lock;
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
ddl_lock_timeout                     integer     0

SQL> alter session set ddl_lock_timeout=10;
Session altered

SQL> 
SQL> INSERT INTO TEST SELECT 1 FROM dual WHERE NOT EXISTS(SELECT * FROM TEST);
0 rows inserted
SQL> COMMIT;
Commit complete
SQL> BEGIN
  2    DBMS_SCHEDULER.CREATE_JOB(JOB_NAME   => 'TEST_JOB',
  3                              JOB_TYPE   => 'PLSQL_BLOCK',
  4                              JOB_ACTION => 'declare
  5      v_date date := sysdate + 10 / 24 / 60 / 60;
  6    begin
  7      loop
  8        dbms_lock.sleep(1);
  9        update test set t1 = t1 + 1;
 10        exit when sysdate >= v_date;
 11      end loop;
 12        commit;
 13    end;',
 14                              START_DATE => SYSDATE,
 15                              ENABLED    => TRUE,
 16                              AUTO_DROP  => TRUE);
 17    DBMS_LOCK.SLEEP(5);
 18  END;
 19  /
PL/SQL procedure successfully completed
SQL> TRUNCATE TABLE TEST;
Table truncated

SQL>