TNS-12203: TNS unable to connect to destination


Sometimes You can get “TNS-12203: TNS:unable to connect to destination  ” error.


Details of error are as follows.

TNS-12203: TNS:unable to connect to destination
Cause: Invalid address specified or destination is not listening.
This error can also occur because of underlying network or network transport problems.
Action: Verify that the net service name you entered was correct.
Verify that the ADDRESS portion of the connect descriptor which corresponds to
the net service name is correct. Ensure that the destination process
(for example the listener) is running at the remote node.



To solve this error, check your the client version if it is compatible with your Database and Listener.
If they are incompatible, then add these two lines to the sqlnet.ora



Or check the firewall settings and disable the firewall as follows.
service iptables stop
chkconfig iptables off

service ip6tables stop
chkconfig ip6tables off

You can disable firewall in Redhat with below script.

systemctl stop firewalld
systemctl disable firewalld



Do you want to learn more details about RMAN, then read the following articles.


About Mehmet Salih Deveci

I am Founder of SysDBASoft IT and IT Tutorial and Certified Expert about Oracle & SQL Server database, Goldengate, Exadata Machine, Oracle Database Appliance administrator with 10+years experience.I have OCA, OCP, OCE RAC Expert Certificates I have worked 100+ Banking, Insurance, Finance, Telco and etc. clients as a Consultant, Insource or Outsource.I have done 200+ Operations in this clients such as Exadata Installation & PoC & Migration & Upgrade, Oracle & SQL Server Database Upgrade, Oracle RAC Installation, SQL Server AlwaysOn Installation, Database Migration, Disaster Recovery, Backup Restore, Performance Tuning, Periodic Healthchecks.I have done 2000+ Table replication with Goldengate or SQL Server Replication tool for DWH Databases in many clients.If you need Oracle DBA, SQL Server DBA, APPS DBA,  Exadata, Goldengate, EBS Consultancy and Training you can send my email adress [email protected].-                                                                                                                                                                                                                                                 -Oracle DBA, SQL Server DBA, APPS DBA,  Exadata, Goldengate, EBS ve linux Danışmanlık ve Eğitim için  [email protected] a mail atabilirsiniz.

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