You should know that it's meaningless to ask for comparison between Access and Oracle because that's not an apple-apple or orange-orange comparison. It's tempting to think of Access as just one other database product but in reality, it's more than just other database product. A better comparison would be comparing Access database engine to Oracle even putting aside the glaring fact that Access database engine is architectured as a file-based database whereas Oracle is a server-based database... those architecture are irreconcilable but both has their places when used correctly.
Finally, neither are exclusive - there are cases where people has used Access as a front-end client to Oracle and that can be a happy combination so there's no need for "vs." comparison especially when we want to use Access as an application, something that Oracle database engine does not provide out of the box... One would need to use Oracle's other offerings (I'm thinking of their application server, JDeveloper, and old Oracle Forms) to fill in the front-end client needs.
So to your question about training - if it's not even used in your workplace anywhere, then I can't see why I as your employer would agree to provide you with training. There's no return for me and it's more likely that I'm just going to speed up your departure once the training is completed and you pick up job that uses Oracle somewhere else. It's a losing proposition for me. So, I think your employer is being prudent.
