Openfire in windows 64,when jvm pass 1G,Must failed,why?

Please help me,when my openfire setup up in windows 64,and my server have 8G RAM,Startup must insert 300,000 relation for chat room and user,but when the JVM pass 1G,openfire is failed,why,how to do?Thank you!

The failed message:

"ETrror occurred during initialization of VMC

h oJuVlMde col dunot reserve enough space for objet nchaetop

be started. The main method may have thrown an exception."

I have solved this problem,this caused by sun jdk1.6,and I replaced it with Oracle JRockit