No you cannot shrink them but more importantly they do not have to be cached. The rest of ibdata1 has to be cached for performance. Impossible to isolate the

No you cannot shrink them but more importantly they do not have to be cached. The rest of ibdata1 has to be cached for performance. Impossible to isolate the caching needs unless undo is moved outside and 99% of servers out there have probably not been setup with external undo logs because most admin do not know of this limitation after it has been configured. Only way around this is to rebuild the entire database, loads of fun.