The RSA-message contains information about requests for global resources (as well as control information). It passes from one system in the ring to another. No system can grant a request for a global resource until other systems in the ring know about the request; your installation, however, can control how many systems must know about the request before a system can grant access to a resource. (See Processing a request for a resource.) The RSA-message contains the information each system needs to protect the integrity of resources; different systems cannot grant exclusive access to the same resource to different requesters at the same time.

When a system receives a request for a global resource, the system suspends the requester and, when the RSA message arrives, places the request in the RSA-message. Systems in the global resource serialization ring batch their requests for global resources. For example, a system might receive seven requests for global resources while waiting for the incoming RSA-message — the message it receives from the preceding system. It adds all seven requests to the outgoing RSA-message — the message that it sends on to the next system in the ring. Batching requests for resources minimizes the communication overhead for global resource serialization.

The order and direction of the RSA-message can change when systems enter or leave the ring. The amount of time that each system holds the RSA-message is called the residency time. Your installation sets the general limits for residency time. While it holds the RSA-message, each system processes the requests in the incoming RSA-message and adds its new requests to the outgoing RSA-message.