Are you
sure username you are about to use is SYSDBA? I, somehow, doubt so.
SYS or SYSTEM seem to be a better choice; while connecting as SYS, there is a need for SYSDBA, though:
Code:
C:\temp>sqlplus sys/pwd
SQL*Plus: Release 10.2.0.1.0 - Production on Pet Ruj 10 23:16:03 2010
Copyright (c) 1982, 2005, Oracle. All rights reserved.
ERROR:
ORA-28009: connection as SYS should be as SYSDBA or SYSOPER
C:\temp>sqlplus sys/pwd as sysdba
SQL*Plus: Release 10.2.0.1.0 - Production on Pet Ruj 10 23:17:11 2010
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Express Edition Release 10.2.0.1.0 - Production
SQL>
Anyway: you'd rather check documentation; it is all described in there.