ORA-01031ORA-01031 . He didn't understand what is causing this. His O/S user was a member of the ORA_DBA group. He tried logging off windows and then logging backup in. Nothing. The solution is actually quite simple. By default, if you install Oracle and don't use the network configuration assistance you get a ORA_HOME without an SQLNET.ORA file. Without it, Oracle will not be able to use O/S authentication. To solve this problem, simply create a file named sqlnet.ora in your ORA_HOME\network\network\admin directory and add to it the following line: SQLNET.AUTHENTICATION_SERVICES = (NTS)