The CMS garbage collector has been removed. `-XX:UseConcMarkSweepGC` and aliases `-Xconcgc` and `-Xnoconcgc` are obsoleted as well as all CMS specific options (too many to list). See [JEP 363: Remove the Concurrent Mark Sweep (CMS) Garbage Collector](https://openjdk.java.net/jeps/363) for more information.