The java launcher currently supports "-mx", "-ms" as equivalent to "-Xmx" and "-Xms". This support is there only for backward compatibility against very old Java versions. Usage of "-mx" and "-ms" (along with some other launcher options) will be deprecated for removal, shortly.

There are some tests in the client-libs area which currently use these options when launching the tests. Those should be updated to use "-Xmx" and "-Xms" instead.