You do not have to specify the same RESMIL value on all systems, but there is no reason to set different values. The only effect of specifying a large value for one system is to increase the RSA-message cycle time, which decreases ring capacity and increases response time. It is simpler to use the same RESMIL value for all systems.

For a complex that consists only of small systems (such as systems running on an IBM® 4381 or only of large systems (such as systems running on an IBM 3090 Model 400E), set RESMIL to the lowest value that works for your complex.

For a complex that includes systems running on both large and small processors, there is a basic problem: the total percent of a small processor's power spent on global resource serialization might be very high because it must process global resource requests generated on all systems.

Setting the RESMIL value differently according to the processor's power does not affect the time (or processor utilization) a system spends processing global resource requests; a system, regardless of the RESMIL value, processes all requests in the incoming RSA-message before it sends the outgoing RSA-message. The RESMIL value affects only the time (or processor utilization) a system spends on ring processing. There is no benefit in trying to use the RESMIL value to adjust for differences in processor power; only the average value is significant.

Thus, use the workload on the large processor to select the RESMIL value and set the same value on all systems. If the workload on the large processor generates many requests for global resources, set RESMIL to a lower value on all systems. Otherwise, make no adjustment for processor power.

The same recommendation applies to a ring where each system runs a distinct workload. Use the workload on the system that generates the largest number of global resource requests as a base for setting RESMIL on all systems.

See Tuning the complex for a description of some techniques you can use to determine the best value for your complex.