We got OutOfMemoryError when upgraded. The JVM settings are kept same as Java 7 which was working fine.
Here is the settings in Jboss 4.2 server:
-server -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000 -Xms4096m -Xmx7168m -XX:MaxMetaspaceSize=512m -XX:+UseConcMarkSweepGC -XX:+CMSClassUnloadingEnabled -Djava.security.egd=file:///dev/urandom
Only difference in Java 7 is XX:MaxMetaspaceSize=512m was replace with PermGen max.
I wonder why it needs more Metaspace for class loading since the server & application is same & only change in Java version.