Sometimes You can get “TNS-12543: TNS:destination host unreachable ” error.
Details of error are as follows.
TNS-12543: 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 ORA-12543: TNS:destination host unreachable.
You should make sure you are trying the right Connection string ( IP or hostname, Port and Service name or SID ).
Do you want to learn more details about RMAN, then read the following articles.