Changing the RNLs for a ring

You can dynamically change the RNLs that global resource serialization uses, as long as the sysplex matches the complex. If your complex has any systems that are not in the sysplex, the change will not take effect. In addition, any single system complex can dynamically change its RNLs.

To change the RNLs currently being used by global resource serialization, set up the GRSRNLxx parmlib members with the new RNLs. Next, issue the SET GRSRNL command on a system that has access to those members. The new RNLs are then communicated to all systems in the complex. Keep in mind that you can not use SET GRSRNL=EXCLUDE or issue SET GRSRNL=xx in a complex already using GRSRNL=EXCLUDE. See Selecting the data for details.

Note: Even though only one system needs the updated parmlib members to start the change, be sure to copy the updated GRSRNLxx parmlib members to each system's parmlib. Any system that needs to can then IPL again into the same complex. Otherwise, the change will be in effect only for the duration of the IPL.

Global resource serialization ensures that the integrity of all resources is maintained throughout the RNL change. In particular, before an RNL change can complete, special processing might be performed if any jobs are using the resources that are different in the old and new RNLs. These resources are known as affected resources. Jobs issuing new requests for these resources are suspended until the RNL change is complete. These are known as suspended jobs. The following message is issued on each system in the complex that has suspended one or more jobs:

ISG210E RNL CHANGE WAS INITIATED BY SYSTEM sysname
        SOME JOBS ARE BEING SUSPENDED UNTIL RNL CHANGE COMPLETES.

If any job currently holds one or more of the affected resources, the change is delayed until all of the affected resources are freed. Jobs holding an affected resource (and thereby delaying the RNL change) are delaying jobs. When jobs are holding affected resources and delaying the change, the following messages are issued on whichever console originated the RNL change:

ISG219E RNL CHANGE WAITING FOR RESOURCES TO BE FREED.
        TO LIST DELAYING JOBS, USE ROUTE SYSNAME,DISPLAY GRS,DELAY.
        TO LIST SUSPENDED JOBS, USE ROUTE SYSNAME,DISPLAY GRS,SUSPEND.
ISG220D REPLY C TO CANCEL RNL CHANGE COMMAND, OR S FOR SUMMARY OF RNL
        CHANGE PROGRESS.

The DISPLAY GRS,DELAY (D GRS,DELAY) operator command lists the jobs that hold affected resources and are causing the change to be delayed. The jobs listed might release the affected resources normally, or they can be cancelled at the discretion of the installation. Once these jobs release the affected resources, the RNL change completes.

The DISPLAY GRS,SUSPEND (D GRS,SUSPEND) operator command lists the jobs that are being suspended due to the RNL change. The jobs listed will remain suspended until the RNL change completes, or until the RNL change is cancelled.

Replying to message ISG220D with an S produces a summary of the RNL change progress. This summary indicates the number of jobs on each system that are delaying or are suspended by the RNL change. Replying to message ISG220D with a C causes the RNL change to be cancelled.

If the operator chooses not to respond to message ISG220D with a C, the change will take place when all delaying jobs release the affected resources.

There may be instances where the operator must either cancel the RNL change command or cancel jobs that hold the affected resources:

A job that is not cancellable is holding affected resources for a long time.
A job holding an affected resource cannot DEQ that resource because it is suspended by global resource serialization pending a new ENQ for another affected resource, or else the job is waiting for some other work in the system that has issued an ENQ for an affected resource and has become suspended.
A job that is suspended by the RNL change is considered more important than the RNL change.

See z/OS MVS System Commands for more information about the DISPLAY GRS and SET GRSRNL commands.