Once the Duplex Established phase has been reached, a subset of all subsequent structure update operations will be transparently duplexed by the system. The Duplex Established phase will exist indefinitely until either a request is issued to stop duplexing (through the SETXCF command or IXLREBLD macro) or as a result of a failure of the duplexing protocol. When duplexing is stopped, an indication of which structure instance should remain allocated is indicated.

During the Duplex Established phase, new users are allowed to connect to the structure, assuming that the connector allows system-managed processes. See Handling Connection Changes During System-Managed Processing.