There are three system parameters (GRS, GRSCNF, and GRSRNL) that indicate to MVS™ at IPL time that a system is to be part of a global resource serialization complex. The GRS and GRSCNF parameters remain in effect for the duration of the IPL, or until they are changed using the SETGRS command. You can change the RNLs without having to reinitialize the entire complex. Use the SET GRSRNL command to accomplish this change. See Changing the RNLs for a ring for more information.

As with all system parameters, there are several ways you can specify the global resource serialization parameters. To minimize operator intervention during IPL, it is generally best to specify GRS, GRSRNL, and GRSCNF in IEASYSxx or take the default values.

You can specify GRS=TRYJOIN in IEASYSxx on each system in the sysplex. If a system is IPLed and there is no complex, that system will start one. If a complex exists, the system joins the complex. The system that starts the complex builds a one-system ring and issues a message stating that a complex is active. As each additional system IPLs, an active system processes the request to join the complex. Global resource serialization writes messages to the system log on the joining system that identify the system that is assisting the joining system.

Global resource serialization also writes messages to the system logs on all systems in the complex to indicate that a new system is joining the ring. These messages indicate that the IPLs are proceeding normally and that the global resource serialization ring can process requests for global resources.