On Microsoft Windows computers
To back up Oracle data on a Microsoft Windows computer, the user account must be configured as follows:
The user account must be a member of both the Local Administrators group and the ORA_DBA group (if OS authentication is used).
The user account must be granted SYSDBA privileges.
Is this account should be the same? Or is it two differetn user? One of the Windows account and one ofe the Oracle admin account?
As you can see, this is a single user that is specified - not two different usernames.
If you are using an account like domain\user then the account must be local admin on the Windows server AND member of the ORA_DBA group.
If you are using an Oracle native user, then it simply needs to have SYSDBA privileges.