Sometimes You can get “TNS-12532: TNS:invalid argument ” error.
Details of error are as follows.
TNS-12532: TNS:invalid argument
You may check the same by trying a telnet to the listener port from the same client where sqlplus connection failed.
$ telnet <db server IP> <listener Port>
The above would return a blank screen with blinking cursor. Note that the above would also fail if you are facing transport issues.
As the underlying cause for the issue is the firewall that has been enabled, take assistance of the network administrator to momentarily disable the firewall on the server host
Once done, re-try the connection from the client host.
There is an unpublished internal bug 6031201 being worked upon by our development team to correct the error code raised from client. Incorrect error message “TNS:invalid argument” being reported is misleading and needs to corrected to something like “TNS:connection refused”
Do you want to learn more details about RMAN, then read the following articles.