Changing the RNL

In certain circumstances, you might need to change the scope of one or more resources. If the sysplex matches the complex, you can use the SET GRSRNL command to make the change dynamically; no system needs to reIPL. If, however, your ring complex includes any systems that are not a part of the sysplex, you must remove those non-sysplex systems from the global resource serialization complex before initiating the change. After the change completes, you can then reIPL the non-sysplex systems back into the global resource serialization complex. Plan your use of the RNL carefully when operating a mixed complex to avoid an unnecessary IPL.

Changing the RNL dynamically would be useful in the following examples:

Add new applications that introduce new resources.
Tune a complex by suppressing reserves, especially against such resources as catalogs.
Reverse an RNL change that might be degrading the performance of your complex.
Change your shared resources (changing local resources into global resources, or changing global resources into local resources).
Run a job (such as DFDSS DEFRAG programs) that performs better with different RNL than the ones used for your installation's normal operations.

After the operator issues the SET GRSRNL command, global resource serialization suspends any job that requests any affected resource (a resource that is not the same in the current RNL as in the new ones) until the change completes or until the operator cancels the change. If a job currently holds one or more of the affected resources, the change is delayed until that job frees any affected resources. For more details see:

Changing the RNLs for a ring for the ring complex, and
Use of the sysplex couple data set and Changing RNLs for a star complex for the star complex.

Some restrictions apply while global resource serialization is processing an RNL change.

Global resource serialization can process only one change command at a time.
The total amount of new RNLs that can be processed during any single change request cannot be greater than 61 KB.
A new system cannot join the complex until after the change completes or is cancelled; however, a system can be removed from the sysplex during an RNL change. If the removed system is the system on which the change command was issued, the change is cancelled.

Note:

After a change completes, you must be sure to update the GRSRNL system parameter (in IEASYSXX) on every system in the sysplex to preserve the changes beyond the next reIPL.
You cannot migrate a global resource serialization ring complex to a star complex during an RNL change.

RNL changes are permanently recorded in SMF records, and RNL change events can be traced using the TRACE CT command with COMP=SYSGRS.