This IBM® Redpaper™ publication reviews performance-related changes introduced in IBM CICS® TS V4.2 that support Java. The paper describes in particular the use of multi-threaded JVM server environments and the support of 64-bit Java 6.0.1 JVMs. This paper is intended for CICS systems architects, administrators, and performance analysts who want to plan, deploy, and monitor these new Java environments.