Support for shared classes is the same when running with, or without, the -Xrealtime option.
The Java™ Virtual Machine (JVM) allows you to share class data between JVMs by storing it in a memory-mapped cache file on disk. Sharing reduces the overall virtual storage consumption when more than one JVM shares a cache. Sharing also reduces the startup time for a JVM after the cache has been created. The shared class cache is independent of any running JVM and persists until it is destroyed.