TNS-12225: TNS:destination host unreachable

Hi,

Sometimes You can get “TNS-12225: TNS:destination host unreachable  ” error.

Details of error are as follows.

TNS-12225: TNS:destination host unreachable

If the Network driver is broken and network is down, you can get this error. So you need to make sure network is up and enabled.

Sometimes you can get this error because of Firewall issues.

Or If database server is down, you can also get TNS-12225: TNS:destination host unreachable.

You should make sure you are trying the right Connection string ( IP or hostname, Port and Service name or SID ).

Or You should check the SElinux settings, SELINUX should be always disabled as follows.

[oracle@msdbadm01 ~]$ cat /etc/selinux/config

# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled - No SELinux policy is loaded.
SELINUX=disabled
# SELINUXTYPE= can take one of three two values:
#     targeted - Targeted processes are protected,
#     minimum - Modification of targeted policy. Only selected processes are protected.
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted

And also check the firewall settings, firewall should be disabled, you can disable it 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.

https://ittutorial.org/rman-backup-restore-and-recovery-tutorials-for-beginners-in-the-oracle-database/