Metro/Global Mirror is a three-site solution, which uses synchronous replication to mirror data between a local site and an intermediate site, and asynchronous replication to mirror data from an intermediate site to a remote site. In this configuration, a Metro Mirror pair is established between two nearby sites (local and intermediate) to protect from local site disasters. The Global Mirror volumes can be located thousands of miles away and would continue to be updated if the original local site has suffered a disaster and I/O has to be failed over to the intermediate site. In the case of a local-site-only disaster, Metro/Global Mirror can provide a zero-data-loss recovery at the remote site as well as at the intermediate site.

Related reading: For additional information about Metro/Global Mirror, see z/OS DFSMS Advanced Copy Services.