DNS导致oracle监听出错 Connection reset by peer
早上起来，研发人员告诉我，数据库无法连接了，我进入数据库查看监听状态
[oracle@lzdb2 ~]$ lsnrctl status
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 23-JAN-2015 09:14:50
Copyright (c) 1991, 2009, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=lzdb2)(PORT=1521)))
TNS-12547: TNS:lost contact
TNS-12560: TNS:protocol adapter error
TNS-00517: Lost contact
Linux Error: 104: Connection reset by peer
发现监听异常，度娘上找了这个问题，发现度娘上的错误，服务器上都没有那些问题，比如什么/etc/hosts下面的127.0.0.1 对应的localhost等，日志文件也未满2G。
突然想到，这个错误就是网络问题
查看网卡配置
# vim /etc/sysconfig/network-scripts/ifcfg-eth2
DNS1=202.98.192.67
发现里面有DNS，想起来了，原来是外部防火墙已经将数据库屏蔽，使数据库无法上网，也就是无法ping通202.98.192.67
将DNS1这条取消掉，重启网卡，查看监听状态
[oracle@lzdb2 log]$ lsnrctl status
LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 23-JAN-2015 09:48:58
Copyright (c) 1991, 2009, Oracle. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=lzdb2)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 11.2.0.1.0 - Production
Start Date 08-DEC-2014 10:36:01
Uptime 45 days 23 hr. 12 min. 57 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Parameter File /u01/app/oracle/product/11.2.2/dbhome/network/admin/listener.ora
Listener Log File /u01/app/oracle/diag/tnslsnr/lzdb2/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=lzdb2)(PORT=1521)))
Services Summary...
Service "orcl" has 1 instance(s).
Instance "orcl", status READY, has 1 handler(s) for this service...
Service "orclXDB" has 1 instance(s).
Instance "orcl", status READY, has 1 handler(s) for this service...
The command completed successfully
监听已正常，使用客户端工具连接正常
总结：当有网卡有DNS配置时，数据库不能连接到DNS导致监听出错，取消掉DNS，重启网卡，监听正常