Shout-out to my homies Chris and Thanh.

 

Depending on how you set up the impersonation settings on your Analysis Services cube’s data source to Oracle, you may run into the following error when trying to process:

 

Login failure: Unknown username or bad password.

 

If you bump into this, open up your data source and choose the Impersonation Information tab. Make sure Default is selected. Next, edit your data source, enter your Oracle credentials and don’t forget to select the save password checkbox.

 

That should do it for you.