Question : Having trouble connecting to Oracle database Error : TNS protocol error 12560

Hello everyone,

I am having trouble getting our application to communicate with the oracle database. The application and database are on 2 separate machines. I can connect to the database using SQL navigator and can run queries on the tables with no issue.

When i try to connect to SQL plus in a DOS prompt using the command SQLPLUS username/password i receive the error TNS Protocol error 12560.

When i specify which SID i want to connect to using the same command SQLPLUS username/password@SID  it will connect fine.

There are 2 oracle instances setup on that server.

I have checked both the tnsnames.ora and sqlnet.ora and they seem to be configured correctly but at this point i am not certain. Any assistance will be greatly appreciated.

Technician

Answer : Having trouble connecting to Oracle database Error : TNS protocol error 12560

It needs to be set the to value in the tnsnames.ora file that you want to be the default connection.