The following variables are used by the module os-java-run for tweaking the JVM settings for container/app startup but are not documented either in module.yaml and README.adoc files:

JAVA_INITIAL_MEM_RATIO= Ratio of maximum memory to use for initial heap size (i.e. -Xms). Defaults to 25% (i.e -Xms=-Xmx*25/100).
JAVA_MAX_INITIAL_MEM= The maximum value of the initial heap size, defaults to 4G.