Group Membership Service
Oracle Parallel Server runs in a multinode environment. In a multinode environment, operating systems typically provide a component called a cluster manager that manages inter-node communication and coordination. Cluster managers are hardware- and operating system-specific. Oracle8 provides a component known as the Group Membership Service (GMS) that communicates with the cluster manager and provides inter-instance initialization and coordination between multiple Oracle instances. A GMS daemon runs on each node. GMS keeps track of instance startup and shutdown in an OPS environment and is notified by the cluster manager of any instance failures. Figure 6.7 shows the relationship between the GMS daemon and the cluster manager on nodes of an OPS cluster.
Figure 6-7. Group Membership Services
Tip
When Oracle8i was released, the functionality provided by GMS was integrated into the Oracle kernel as the Cluster Group Service, and also into vendor-specific cluster managers. Consequently, in Oracle8i, the GMS daemon no longer exists.
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