This would be a question for the EBS space General EBS Discussion ,
But the platform of your application server should not need to be the same as your DB server, as long as they can communicate using the network fine. I'm not sure if EBS will make any difference but it's EBS and anything can happen.
Currently my EBS 11.5.9 apps is on HPUX 11.11.
My 9i EBS database is on HPUX 11.23.
The DB server is running on maximum capacity now. There is a plan to migrate 9i EBS database from HPUX to Solaris 10 which is new and much powerful server.
Can we migrate the database from HPUX to Solaris and remain the Apps on HPUX platform?
Does the Apps and DB need to be on same platform?
Since both 9i and 11.5.9 are in sustaining support, this project is fraught with unknown pitfalls and issues.