How does DCEVM patch the JVM so that it can be started both in the normal mode and in XXaltjvm mode? What does it do to the regular libjvm.so/jvm.dll/libjvm.dylib?
From Installing DCEVM
DCEVM does not patch the original JVM.
It installs a different version of libjvm.so under $JDK_HOME/lib/dcevm
-XXaltjvm option is supported by the regular Java launcher out of the box. When specified, the launcher looks for libjvm.so in the alternate directory:
-XXaltjvm value starts with /, it is treated as the absolute path of the alternative JVM;$JDK_HOME/lib/<altjvm>