What makes you think you need to resort to an AUTONOMOUS transaction? Are you aware of it's caveats?
There usually is no reason to use an AUTONOMOUS transaction, other then wrong reasons like bypassing mutating table errors, committing in triggers etc.
I truly hope you're not implementing for reasons as such, since you can end up with corrupted data or other strange errors.
Application logs that do not disappear at rollback time ?
Yes - that is a common and acceptable use of the pragma.
See my reply in this thread for sample code illustrating use of the pragma for a logging package.