Oracle database monitoring is very slow, basic hang fault handling

Today I found the database connection is very slow, even can not connect, want me to check to see

#su - oracle$ lsnrctl statusLSNRCTL for Linux: Version 11.2.0.1.0 - Production on 17-MAY-2018 12:29:11Copyright (c) 1991, 2009, Oracle.  All rights reserved.Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=oracletest)(PORT=1521)))    ## 到这里，hang住了，一直没有响应

A tnsping test was made from another host:

[email protected]:/u01/app/oracle/11.2/db_1/network/admin> tnsping oracletestTNS Ping Utility for Linux: Version 11.2.0.1.0 - Production on 17-MAY-2018 12:54:20Copyright (c) 1991, 2009, Oracle.  All rights reserved.Used parameter files:Used TNSNAMES adapter to resolve the aliasAttempting 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

Finally, when the DNS configuration is checked, it is found that:

 # 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。

In fact, you can consider opening listener trace for viewing.

or modify the sshd configuration file Usedns parameter to No, DNS is not resolved

#vi /etc/ssh/sshd_configUseDNS no

This does not matter even if the/etc/resolv.conf system configuration DNS is retained.

Oracle database monitoring is very slow, basic hang fault handling