仔细看了问题，发现sdh_ora_29241.trc这个dump文件在我重启服务器之前一直在扩大，然后是本地能连上数据库，二通过监听则不能连接数据库。重启后正常。

alert.log如下：

Wed Dec 15 08:02:41 2010

Errors in file /oracle/app/oracle/admin/sdh/udump/sdh_ora_29241.trc:

---此文件sdh_ora_29241.trc有3G大

ORA-12570: TNS:packet reader failure

Wed Dec 15 09:17:25 2010

Failure to extend rollback segment 27 because of 3113 conditionFULL status of rollback segment 27 set.

Wed Dec 15 09:38:52 2010

Failure to extend rollback segment 30 because of 3113 conditionFULL status of rollback segment 30 set.

故障记录于此，待分析。。。

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由于此问题现象没找到对应的故障解决方案，咨询oracle，提出了监控方案，记录如下，待下次故障发生

Can you able to reproduce this issue If yes please do provide the following,

Please set the following parameter in sqlnet.ora (server / client side) and then reproduce the error.

To enable SQL*Net tracing, add the following lines to $ORACLE_HOME/network/admin/sqlnet.ora on the machine:

Server (add to server’s sqlnet.ora):

trace_level_server=16

trace_directory_server=*

trace_file_server=*

(or)

Client (add to sqlnet.ora):

trace_level_client=16

trace_directory_client=*

trace_file_client=*

and upload the trace file