Use the ACCELSYS option in GRSCNFxx to specify ring acceleration and the number of systems that must see a resource request before it is granted.

Without ring acceleration, every system in the ring must see each request for a global resource. While the RSA-message makes a complete cycle around the ring, the task that requested the global resource is suspended. This processing guarantees the integrity of resources; no global resource request is granted until all systems know about it. It does, however, mean that every task that requests a global resource must wait for at least one RSA-message cycle.

Ring acceleration offers an alternative technique, which protects the integrity of resources while potentially providing a significant reduction in global resource request response time (the time a task is suspended while waiting for ring processing).

Ring acceleration requires alternate links, used to send the ring acceleration signal from one system to another. In addition, IBM® suggests that the complex be a fully-connected complex. Using ring acceleration can significantly improve ring performance in large complexes; in two-system complexes, it provides minimal benefits.

Figure 1 shows an example of a complex that could use ring acceleration. It is a fully-connected four-system complex with primary links, shown as heavy lines, and alternate links, shown as light lines.

Figure 1. Ring Acceleration Configuration