"You're comparing an OS independent language to an entire operating system?" No, I am not comparing Java, but JVM. JVM is a platform, so it should have insight

"You're comparing an OS independent language to an entire operating system?" No, I am not comparing Java, but JVM. JVM is a platform, so it should have insight what's happening on it, don't you think? Whether this insight comes from the platform (JVM or z/OS) or the underlying system (native host OS or mainframe) is irrelevant - you probably want both (and in z/OS you get both). Whether Java (the language) is clunky is irrelevant - z/OS has lot clunkier languages on it (application development is huge pain on z/OS compared to JVM), and I still think z/OS beats JVM for large/complex/maintainable systems. ;-) (Basically for the same reason - more mature.) z/OS has many logging and tracing functions, at different granularity, some of them are assisted with mainframe hardware. I don't see how JVM could beat it, but I may be wrong.