在10.2.0.5上创建实例，配置EM的时候报错，忽略它后，库能正常登入，但EM不正常。之后在其他10.2.0.5的环境上又重试了一次，发现依然有这个问题，在10.2.0.1上没问题，于是怀疑是oracle的一个bug，查询了MOS，果然有这个。patch号为8350262。
Oracle对此的解释是：
In Enterprise Manager Database Control with Oracle Database 10.2.0.4 and 10.2.0.5, the root certificate used to secure communications via the Secure Socket Layer (SSL) protocol will expire on 31-Dec-2010 00:00:00. The certificate expiration will cause errors if you attempt to configure Database Control on or after 31-Dec-2010. Existing Database Control configurations are not affected by this issue.
If you plan to configure Database Control with either of these Oracle Database releases, Oracle strongly recommends that you apply Patch 8350262 to your Oracle Home installations before you configure Database Control. Configuration of Database Control is typically done when you create or upgrade Oracle Database, or if you run Enterprise Manager Configuration Assistant (EMCA) in standalone mode.
可以查看：Enterprise Manager Database Control Configuration - Recovering From Errors Due to CA Expiry on Oracle Database 10.2.0.4 or 10.2.0.5 [Video] [ID 1222603.1]
解决方法：
如果是在创建实例前就已经打了这个patch的话，那之后就不会报错了。如果是在创建实例之后才打的这个patch，那么需要执行以下：
对于单实例：
1.使用Opatch安装Patch 8350262
2.设置ORACLE_HOME and ORACLE_SID 环境变量，执行 <PATCH_HOME>/killDBConsole.(windows 平台省略这一步)
3.Re-secure Database Control with the following command:
<ORACLE_HOME>/bin/emctl secure dbconsole -reset
4.Re-start Database Control with the following command:
<ORACLE_HOME>/bin/emctl start dbconsole
对于RAC：
1.使用Opatch安装Patch 8350262, 在一个节点安装就ok了。
2.在所有节点执行：设置ORACLE_HOME and ORACLE_SID 环境变量，执行 <PATCH_HOME>/killDBConsole.(windows 平台省略这一步)
3.Re-secure Database Control on the first cluster node with the following command:
<ORACLE_HOME>/bin/emctl secure dbconsole -reset
4.Re-secure Database Control on the remaining cluster nodes with the following command. Note that the -reset switch is not included with this command:
<ORACLE_HOME>/bin/emctl secure dbconsole
5.Re-start Database Control by executing the following command on each node in the cluster:
<ORACLE_HOME>/bin/emctl start dbconsole