Oracle数据库监听非常慢，基本hang住故障处理

测试人员邮件反馈：
 订购数据库的连接非常慢，甚至是无法连接，想要我检查看看。

经查看：
 Oracle@wdatest11:~/app/admin/wdadb/adump> lsnrctl status

LSNRCTL for Linux: Version 11.1.0.7.0 - Production on 17-JUN-2014 18:15:47

Copyright (c) 1991, 2008, Oracle.  All rights reserved.

Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=wdatest11)(PORT=1521)))  ## 到这里，hang住了，一直没有响应

从其他主机做了个tnsping测试：
 oracle@IBlvs02:/u01/app/oracle/11.2/db_1/network/admin> tnsping wdatest
 

TNS Ping Utility for Linux: Version 11.2.0.3.0 - Production on 17-JUN-2014 17:53:20
 

Copyright (c) 1997, 2011, Oracle.  All rights reserved.

Used parameter files:
 

Used TNSNAMES adapter to resolve the alias
 Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.121.134)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = wdadb)))
 OK (14760 msec)    ## 可见响应也是非常慢的。
 

oracle@IBlvs02:/u01/app/oracle/11.2/db_1/network/admin> tnsping wdatest
 

TNS Ping Utility for Linux: Version 11.2.0.3.0 - Production on 17-JUN-2014 17:54:20
 

Copyright (c) 1997, 2011, Oracle.  All rights reserved.
 

Used parameter files:
 

Used TNSNAMES adapter to resolve the alias
 
Attempting to contact (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.121.134)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = wdadb)))    ## 这里也是hang住，一直没有响应

最后检查DNS配置时，发现有：
 wdatest11:~ # cat /etc/resolv.conf
 nameserver 211.141.90.68
 系统配置有DNS，这是内网主机，根本用不到DNS，所以把这个DNS去掉后恢复正常。
 其实可以考虑开启listener的trace进行查看的。

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