SQL*Plus TNS:protocol adapter error I am using this system on which everything was already configured. I want to connect to local db on SQL Plus. When I enter user-name scott and password tiger, it gives ORA-12560:TNS:protocol adapter error.

Enter user-name: scott
Enter password:
ERROR:
ORA-12560: TNS:protocol adapter error


When I try with one line connection string scott/tiger@localhost:1521/orcl, it gives ORA-12541: TNS:no listener.

Enter user-name: scott/tiger@localhost:1521/orcl
ERROR:
ORA-12541: TNS:no listener


I am new to this.
Please make sure that oracleserviceSID is running in your services.msc.

Then try restart your listener from services.msc itself or from command prompt(connect to sqlplus sys as sysdba).

(Hope you have configured listener.ora from netca)