If you have forgotten the SYSTEM / SYS password of Oracle Database, it is possible to set it from sqlplus command prompt window.
1. Login to the Windows machine as an Administrator where the database is installed.
2. Start > Programs > Oracle – Instance Home Name -> Application Development > SQL Plus
4. ALTER USER SYS IDENTIFIED BY ADMIN123; (replace ADMIN123 with your password) and press enter. You should see “user Altered” message.
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