November 18, 2010

Connecting to the Oracle Database Listener is extremely slow

This note really applies to any version of the Oracle Database on Linux.


Any connection through the database listener is extremely slow. It works fine, but it is not unusual for connection to take over a minute.

I try to start the listener as follows:
oracle@soa11gdev:/u01/app/oracle/product/11.2.0/db_1> lsnrctl start
It starts up after several minutes, instead of a few seconds.

Once it's up, I try to ping the listener as follows:
oracle@soa11gdev:/u01/app/oracle/product/11.2.0/db_1> tnsping orcl
The response is over 60 seconds.

When I try to sqlplus into the database through the listener, it takes over 60 to 70 seconds:
oracle@soa11gdev:/u01/app/oracle/product/11.2.0/db_1> sqlplus system/manager@orcl
Trying to sqlplus to the database directly (i.e., bypassing the listener) is fine:
oracle@soa11gdev:/u01/app/oracle/product/11.2.0/db_1> sqlplus system/manager
The thing is, the listener works and is not misconfigured. But connecting is exceptionally slow.


Check your $ORACLE_HOME/network/admin/sqlnet.ora configuration file and ensure that the TNSNAMES is specified first as follows:
In my case, the database was installed on Oracle Enterprise Linux 5.5.

My hostname was set to the fully qualified name of "" and my /etc/hosts had the following entry:    oradev

The problem is that /etc/resolv.conf had an incorrectly configured search domain.

Original /etc/resolv.conf:
search localdomain
Corrected /etc/resolv.conf:
Once this was corrected, problem was solved.

Applicable Versions:
  • Oracle Database 11g (11.2.0) 32-bit and 64-bit
  • Oracle Enterprise Linux 5.5 32-bit and 64-bit