Enter "sqlplus / as sysdba" in the command window and press Enter to connect to Oracle
E.g
C:\>sqlplus / as sysdba
SQL*Plus: Release 11.2.0.1.0 Production on Tue Apr 17 10:05:34 2012
Copyright (c) 1982, 2010, Oracle. All rights reserved.
www.2cto.com
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL>
So what exactly does this command do? You might as well log in and enter "select user from dual;" to check, and you can see the following results:
C:\>sqlplus / as sysdba
SQL*Plus: Release 11.2.0.1.0 Production on Tue Apr 17 10:11:11 2012
Copyright (c) 1982, 2010, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
www.2cto.com
SQL>
select user from dual;
USER
------------------------------
SYS
SQL>
Obviously we just logged in as the SYS user
This means that the username and password are omitted here.
We then log in as "sqlplus sys/**** (the password of the sys user) / as sysdba". At this time, no matter whether the user name or
password
exists in the system, we can log in normally. The logged in user is still "SYS". The command operates as follows:
C:\>sqlplus sss/sss as sysdba
SQL*Plus: Release 11.2.0.1.0 Production on Tue Apr 17 10:21:12 2012
Copyright (c) 1982, 2010, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
www.2cto.com
SQL> select user from dual;
USER
------------------------------
SYS
SQL>
Command details: When logging in with sqlplus / as sysdba, the operating system authentication method is used, so entering the username/password is the same as not entering it.