how to connect to a oracle user without knowing the password

http://oracledb101.wordpress.com/2013/09/12/connecting-to-a-schema-without-knowing-the-password/

We are going to allow the SCOTT username to be able to login as the APEX_030200 user.  Both accounts have already been created as normal database accounts. A simple alter user command is need to allow SCOTT to login as APEX_030200.

$sqlplus / as sysdba
sqlplus> alter user APEX_030200 grant connect through scott;

User altered.