To bring a CTC link online or take a CTC link offline, use the VARY command. All links that you want global resource serialization to use must be defined in the GRSCNFxx member.

To bring a defined link online, issue VARY devnum,ONLINE. In response to this command, the link comes online, and global resource serialization changes its status from DISABLED to ALTERNATE. It is then available to send the ring acceleration signal or to act as a backup for a primary link.

To take a defined link offline, issue VARY devnum,OFFLINE. In response to this command, the link goes offline, and global resource serialization changes its status from ALTERNATE to DISABLED. The specified link must be an alternate link; if an operator tries to take the primary link offline, global resource serialization rejects the command.