I install toad in my computer.but when try to log in It askes me database,user name & password.I have installed oracle 9i to my system.So i choose database name ra user : ora password ra but i got an error :"ORA-125 : TNS :no listener" why I get this error? how can I fix it?
Since you have installed toad that would imply you have a Windows system.
In this case Oracle is installed as a service called OracleService<SID>, where <SID> is the System Identifier of your database. In your case OracleServiceORA. Make sure this service is started. The listener is another service called (as far as I can remember) Oracle<ORACLE_HOME_NAME>TNSListener where <ORACLE_HOME_NAME> is the value you chose on installation. Make sure this service is started.
If you are on *nix tell me because the steps are different.