第三步報錯ORA-00054和LOCK table無關，
而是和和第二步insert沒有送出有關。
insert已經其他DML語句執行的時候會給相關對象加個TM鎖，以防止該對象再被操作的時候(DML--資料操控語言)發生結構改變，即使DDL語句。
SQL> create table t1 (c1 char(2));
Table created.
SQL> select userenv('SID') from dual;
USERENV('SID')
--------------
1596
SQL> insert into t1 values('1');
1 row created.
SQL> select type,id1,id2 from v$lock where sid='1596';
TY ID1 ID2
-- ---------- ----------
AE 100 0
TM 593805 0
TX 3670041 37004435
3 rows selected.
SQL> select object_name from dba_objects where object_id=593805;
OBJECT_NAME
------------------------------
T1
1 row selected.
這時候在另外一個會話裡
SQL> truncate table t1;
truncate table t1
*
ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired
SQL> lock table t1 in exclusive mode nowait;
lock table t1 in exclusive mode nowait
*
ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired
SQL> lock table t1 in exclusive mode; --一直等待，
lock table t1 in exclusive mode
*
ERROR at line 1:
ORA-01013: user requested cancel of current operation --使用者手動終止
SQL> alter table t1 add (c2 number); --一直等待
alter table t1 add (c2 number)
*
ERROR at line 1:
ORA-01013: user requested cancel of current operation --使用者手動終止