You can use the RVOLUME command to join volumes to the session anytime after the session ID is defined to the LSS where the volume resides. Once the session is started, you can add or remove volumes in the session, however, the only volume that can be added is the primary of the PPRC pair. Primary volumes may be added to a session in any state: simplex, pending, duplex, or suspended. If a volume joined to a session has not yet completed its initial copy, or if the proper FlashCopy® relationship has not been established from the PPRC secondary to a target, its status in the session will be "join pending" and it will not participate in consistency group formation until the initial copy is completed. If a volume added to a session is the primary of a suspended pair, the first attempt to form a consistency group will fail, so this is strongly discouraged.
In a multi-target environment, only one of the pairs can
participate in a Global Mirror session. The secondary needs to be identified at join time.