Coordinating remote copy status changes across multiple logical sessions to maintain consistency

Abstract

A multi-session data storage facility coordinates similar status changes across all sessions at appropriate times. In each session, a data mover implements data mirroring by copying updates from the primary storage to the secondary storage. A master data set, accessible by all sessions, includes a common area for posting commands and/or errors to all sessions and individual session areas for posting errors occurring in particular sessions. When a data mover receives a host initiated command, this data mover becomes a “master.” Initially, the master data mover lists the command in the master data set's common area. Whenever other, “slave” data movers notice a command in the master data set's common area, they respond by suspending their formation of consistency groups and responding with a “ready” message. The “ready” message comprises the slave data mover's consistency form time (i.e., the earliest of most-recent update time from all controllers in that session). Accordingly, after posting the command, the master data mover reviews the slave data movers' responses. If these responses indicate all sessions can execute the command at a requested consistent time, then the master data mover instructs the slave data movers to execute the command by entering an execute instruction in the master data set's common area. Otherwise, the master data mover enters a cancel operation in the master data set's common area.