Wednesday, July 3, 2013


Today we handed over a newly created database on a newly built server to application team for their testing and operations. We completed all the procedures before handing over the database to the apps team which includes registering of database in the listener. Application team started to log in to the system using SQL Developer to get the following error.

Application team members called us to help them resolve the issue. So at the first glance I couldn't guess anything regarding the issue as it states IO Error. So I took the case and tried to figure out what is wrong with this. 

I tried to ping the server from my system remotely to which it was successful.

Next step is to edit the tnsnames.ora file to include the tns entry for the connection and try tnsping. Now I tried tnsping from my system after editing the tnsnames.ora file but to get an error.

This error says destination host unreachable.
Checking the host server and the listener status.

We just pinged the server and also listener is running fine on the server and also we are able to connect to the database using connect string from the same server as below.

A general search on the Oracle support docs gave the exact problem, cause and the solution.
MOS note id “TNSPING fails with TNS-12543: TNS:destination host unreachable [ID 1556918.1]” suggested the cause as
This might be a network issue with either the underlying transport not being able to contact the host, or a firewall is blocking this client or connection.
Make sure the network is functioning correctly.

So the fix would be to contact the OS/Network admin. Hence I involved the OS admin to fix the networking issue after explaining what’s happening with the issue.

OS team then confirmed that iptables process is running on the server which is a firewall package in Linux. So once after stopping the iptables process, we are now able to connect to the database from remote servers.

The problem is resolved. :-) Happy troubleshooting!!


  1. >> stopping iptables

    Not the best solution, unless the *only* service running on the host is the database instance.

    Better to add an exception for the database port number, keep blocking for all other unused ports. Especially if the server is or will be placed out in the DMZ.

    1. Hi,

      Thank you for the suggestion posted. It is the dedicated server for database alone. I'll keep the valuable suggestion provided in my list of knowledge gathered.

      Thank you again!!


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