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Sets an initial size for an area in memory that is reserved for any native classes, monitors, and threads that are used by compressed references within the lowest 4 GB memory area.

You can use the -verbose:sizes option to find out the value that is being used by the VM.


  • Native memory OutOfMemoryError exceptions might occur when using compressed references if the lowest 4 GB of address space becomes full, particularly when loading classes, starting threads, or using monitors.
  • If you are not using compressed references and this option is set, the option is ignored and the output of -verbose:sizes shows -Xmcrs0.



See Using -X command-line options for more information about the <size> parameter.