1、出现问题：
1）后台alter日志没有任何错误
2）mmon报错内容如下
*** KEWRAFC: Flush slave failed, AWR Enqueue Timeout
*** 2013-02-17 10:46:15.419
*** KEWRAFC: Flush slave failed, AWR Enqueue Timeout
*** 2013-02-17 10:47:15.598
*** KEWRAFC: Flush slave failed, AWR Enqueue Timeout
*** 2013-02-17 10:48:15.783
*** KEWRAFC: Flush slave failed, AWR Enqueue Timeout
*** 2013-02-17 10:49:15.968
3）做awr报告是，没有最近的snapshot生成
2、问题排查：
1）查看锁和session
select do.object_name,
do.object_type,
gv.SQL_ID,
gv.EVENT,
gv.WAIT_CLASS,
gv.WAIT_TIME,
gv.PADDR
from gv$locked_object gl, gv$session gv, dba_objects do
where gl.SESSION_ID = gv.SID
and gl.OBJECT_ID = do.object_id;
发现有awr相关的表锁住了
2）查看锁表的进程
select * from gv$process gp where gp.ADDR='00000002D8610778';
3）使用os命令
# ps -ef | grep 28039
oracle 28039 1 0 04:00 00:00:16 ora_m000_west1
kill 掉m000就恢复正常