You can change the properties of the Database Manager operator (DBM operator) and the database system administrator (SYSDBA user).
...
1. Choose Instance ® Configuration ® DBM User...
2. Select a user.
3. Choose Properties.
4.
Choose the
General tab page and change the required properties.
If you want to change passwords, you might have to transfer the database
instance to the relevant operational state. See Changing the Password
of a DBM Operator