Hello.
After several surveys, the problem is the openfire on windows. Even with windows 64bit, the survey, can manage a maximum 1.5gb per process.
So, I prepared another server with Centos Linux and java 64bit. Moved the jre folder / opt / openfire to jre.old and changed the parameter OPENFIRE_OPTS = Xmx4096 which is in the / etc / sysconfig / openfire because it was installed .RPM. Remembering that I left with mysql database.
I test with 6Gb and functioned normally.
In summary: It windows restriction.
Regards,
Antonio.