After installation of Oracle 9i on Windows XP, when I try to log in using "scott/tiger," it's not logging in and displaying the message "Enter user-name," and for the third time it's coming out of SQL. Error: "ORA-12560." I am not entering any hostname as it's a workgroup machine.
This error is often difficult to diagnose because it can point to different problems. It sounds like you are trying to connect locally to a database that is running on a Windows XP machine. The first thing you will want to check is that the database is open and available. Second, if you are invoking SQL*Plus from the DOS command prompt, you should first set your ORACLE_SID to the database you wish to connect to, especially if you are not providing a service name (e.g., sqlplus scott@oradev01). To set your SID (be sure to replace ORADEV01 with your SID):
The echo command should return the SID that you specified in the previous set command. Ensure there are no spaces on either side of the equal sign when you set ORACLE_SID.
If you are providing a service name, ensure that the listener has been started. It is also a good idea to check the sqlnet.log file. This may also give you some indication of what the problem is.
Finally, this error can occur if you created a database with a SID that contains a non-alphanumeric character, e.g., underscore. You will not be prevented from creating a SID with a non-alphanumeric character and the service will start successfully; however, you may see this error when trying to connect to the database.
This was first published in July 2005