Oracle通过SQL加载程序插入数据时出错

-- session 1 (no commit)
SQL> delete from t where rownum = 1;
1 row deleted.
-- session 2
SQL> truncate table t;
truncate table t
*
ERROR at line 1:
ORA-00054: resource busy and acquire with NOWAIT specified or timeout expired
SQL> alter session set ddl_lock_timeout = 10;
Session altered.
SQL> truncate table t;
[waiting waiting.... somewhere in here we commit in session 1]
Table truncated.