http://www.dba-oracle.com/t_passwords_locking_changing_expiring.htm
There are many users on a full installation of Oracle, most of which you probably won't need. To lock an Oracle user account, you can use the following command:
alter user username account lock;To unlock the user, simply replace 'lock' with 'unlock'.Oracle comes with a few default accounts that should never be locked or dropped. These include: SYS, SYSTEM, SYSMAN (Oracle 10g), OUTLN(can't?). However, you do want always to change the password for these users. The default password for SYS is change_on_install. It is important that you follow these directions. To change the password for a user:alter user username identified by new_password;For non-critical users, you can always lock and expire the account. We can change the password for, lock, and expire the account CTXSYS all at once:alter user ctxsys identified by 0bscur3 account lock password expire;This will ensure that CTXSYS password has been changed from the self evident default of CTXSYS; on a successful login the password will have to be changed (because it is expired); and because it is locked, he account can't be logged into under any circumstances.To aid you in this task, here is a list of users that come with a full database installation that are safe to expire and lock if you are not using their functionality:AURORA$ORB$UNAUTHENTICATED - Jserver user BI - demo user CTXSYS - Oracle Text/interMedia administrator DBSNMP - Oracle Intelligent Agent DSSYS - Dynamic Services and Syndication Server HR - demo user MDSYS - Spatial administrator ORDSYS/ORDPLUGIN - Object Relational Data user OE - demo user PERFSTAT - Statspack administrative user SCOTT - demo user SH - demo user TRACESVR - Oracle trace server WKSYS - Ultrasearch administrator The best rule of thumb is to install only the features you need when you install Oracle. If you are not going to use Spatial, interMedia, or UltraSearch, don't install them. Then you will not have to worry about those three users.
