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

FROM http://blog.csdn.net/jgmydsai/article/details/10523969

 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>