If any of these measurements reveal problems, the most important and useful action is to change the RESMIL value. Divide the change equally among all systems. There is no need to have a different RESMIL value for each system. Residency time value (RESMIL) and RESMIL value contain more detailed information.

If your major area of concern is the response time for global resource requests (that is, your concerns are resource availability or delays for work because of ring processing), you can reduce the cycle time by reducing the RESMIL value for each system. Reducing the cycle time reduces the time global resource serialization requires to process each request for a global resource and makes the complex more responsive to individual resource requests. Reducing the cycle time, however, increases the number of times the system must process the RSA-message per second; it thus tends to increase the global resource serialization overhead — the demands it makes on the processor, channels, and devices.

If your major area of concern is the system overhead that global resource serialization causes (that is, your concern is system throughput), you can increase the cycle time by increasing the RESMIL value for each system. Increasing the cycle time reduces the system overhead. It decreases the number of times the system must process the RSA-message per second and thus tends to decrease the demands global resource serialization makes on the processor, channels, and devices. A longer cycle time, however, tends to increase the time global resource serialization requires to process each request for a global resource and makes the complex less responsive to individual requests for global resources.

There are two other basic tuning actions. One is to reduce the number of requests for global resources that the complex must process. That is, you want to ensure that all resources processed as global resources actually require global serialization. To reduce the number of requests for global resources, place entries in the SYSTEMS exclusion RNL to exclude from global serialization those resources, such as temporary data sets, that require only local serialization.

Another basic action is to convert as many reserves as possible. This action does not directly affect the performance of the complex, but it does increase the availability benefits your installation gets from the complex. Therefore, consider developing a long-term plan to work toward the goal of increasing the number of reserves converted to requests for global resources. For example, if you cannot convert reserves only because a volume can be accessed both by systems in the complex and systems outside the complex, change your use of the volume so that only systems in the complex can access it. You can then convert the reserves.