Book excerpt: This IBM Red paper books publication presents Workload Partitions (WPARs), a set of completely new software-based system virtualization features introduced in IBM AIX Version 6.1. Adding WPARs to the AIX operating system provides a new level of system virtualization capability. WPARs complement the already existing AIX and System p virtualization features, by allowing: - The partitioning of an AIX instance into multiple environments, each hosting applications and providing isolation from applications executing in the other environments - The ability to checkpoint and restart execution of applications without modification of the application code - The capability to relocate a live application into a different AIX instance, whether it is hosted in an LPAR of the same physical server or executing on a different physical server - Fine-grained control of resource utilization by each application executing within an AIX instance