In oracle you might get an error while connecting
ORA-12561 : TNS: Protocol adapter error
This error usually come when the required oracle service is not installed or started
To fix this error just follow the following steps
1. Go to services by typing services.msc
(You must be a Administrator to perform this)
Now find service name "OracleServiceORCL"
2. Right click on this service and click on Properties
3. Now set startup type to Automatic
4. Below the service status label just click on Start Button
You are done now you can connect to SQLPLUS easily.
If you have any queries than please do comment