All z/OS® Communications Server coupling facility structures support system-managed duplexing. This allows two copies of the structure to be created for backup purposes. Updates to the structure are automatically kept in sync so if access to one of the structures is lost, the other copy is used without any disruptions. To create a duplexed copy of the structure, use the SETXCF START,REBUILD,DUPLEX command. To stop duplexing and return to a single allocated structure, use the SETXCF STOP,REBUILD,DUPLEX command. For more information about the SETXCF command, see z/OS MVS System Commands.