Book excerpt: IBM® z/OS® Global Mirror (zGM), also known as Extended Remote Copy (XRC), is a combined hardware and software solution that offers the highest levels of continuous data availability in a disaster recovery (DR) and workload movement environment. Available for the IBM DS8000® Storage System, zGM provides an asynchronous remote copy solution. This IBM RedpaperTM publication takes you through best practices for planning, tuning, operating, and monitoring a zGM installation. This publication is intended for clients and storage administrators who need to understand and maintain a zGM environment.