IBM® WebSphere® Application Server (WAS) version 7.0 introduces compressed reference (CR) technology to dramatically improve WAS performance on 64-bit platforms.
IBM CR technology for Java™ allows 64-bit WAS deployments to allocate large Java heaps without the memory footprint growth and performance overhead generally incurred with larger, 64-bit address references. Using CR technology, WAS instances can allocate heap sizes up to 28GB 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.