If you have a process that takes 2 mins to run, that is something that I would recommend making a process you run via dbms_scheduler and letting the user know when the process is completed as apposed to having them sit there waiting for it to complete...
I agree that perhaps the user should not wait that long for the page to come back, but to answer your questions.
Edit your button, change the Action from Submit to Redirect to URL.
Use a code like this:
Change SAVE to the correct request value.