The 64–bit server, available on Solaris SPARC and AMD64 platforms only, is more scalable than the 32–bit version. You can use the 64–bit server if your system has more than 4 GB of RAM. Some of the advantages which the 64–bit server has over the 32–bit server are:
More file cache for static content
Many simultaneous servlet sessions because of the 64–bit JVM