IBM® WebSphere® Application Server version 7.0 introduces compressed reference technology to dramatically improve WebSphere Application Server performance on 64-bit platforms.
IBM compressed reference technology for Java™ allows 64-bit WebSphere Application Server deployments to allocate large Java heaps without the memory footprint growth and performance overhead generally incurred with larger, 64-bit address references. By using compressed reference technology, WebSphere Application Server instances can allocate heap sizes up to 28 GB with the same physical memory overhead as an equivalent 32-bit deployment.
For more information, see IBM WebSphere Application Server WAS V7 64-bit performance - Introducing WebSphere Compressed Reference Technology.