The GRS= system parameter indicates to MVS™ at IPL time that a system is to be part of a global resource serialization star complex. The GRS and GRSCNF parameters remain in effect for the duration of the IPL; the only way to change their value is to IPL the system again. You can change the RNLs without having to reIPL the entire complex. Use the SET GRSRNL command to accomplish this change. See Changing RNLs for a star complex for more information.

Many values in the GRSCNF parmlib member can be changed without re-IPLing the system. See the SETGRS command in z/OS MVS System Commands for the complete list.

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 the IEASYSxx parmlib member or accept the default values. See Defining parmlib members for a star complex.

You can specify GRS=STAR in IEASYSxx on each system in the sysplex. The first system in the star sysplex to initialize will initialize the global resource serialization lock structures on a coupling facility to start the star complex. See z/OS MVS Setting Up a Sysplex.