--session 1
11:32:23 SQL> delete from t_xifenfei where username='CHF';

0 rows deleted.

Elapsed: 00:00:00.00

--session 2
SQL> set time on
11:34:10 SQL> set lines 150
11:34:17 SQL> show parameter ddl_lock_timeout;

NAME                                 TYPE                   VALUE
------------------------------------ ---------------------- --------
ddl_lock_timeout                     integer                0

11:34:19 SQL> alter table t_xifenfei add (xff varchar2(10));
--hang住


--session 1
11:34:35 SQL> commit;

Commit complete.

Elapsed: 00:00:00.00

--session 2结果

Table altered.

11:37:46 SQL> 

设置ddl_lock_timeout未生效

--session 1
11:37:41 SQL> delete from t_xifenfei where username='CHF';

0 rows deleted.

Elapsed: 00:00:00.01

--session 2
11:40:58 SQL> alter session set ddl_lock_timeout=10;

Session altered.

11:41:07 SQL> alter table t_xifenfei add (xff_n  varchar2(10));
--hang住

--session 1
11:41:14 SQL> commit;

Commit complete.

Elapsed: 00:00:00.00
11:42:48 SQL> 

--session 2
Table altered.

11:43:37 SQL> 

试验证明,在增加新列时,ddl会话不会报ORA-00054错误,同时ddl_lock_timeout参数也未生效