Veritas Storage Foundation 5.1 SP1 for Oracle RAC Administrator"s Guide (5900-1512, April 2011)

Group Membership Services/Atomic Broadcast

The GAB protocol is responsible for cluster membership and cluster

communications.

Figure 1-6 shows the cluster communication using GAB messaging.

Figure 1-6

Cluster communication

Node 1 Node 2

GAB Messaging

Datafile Management

File System Metadata

Volume Management

Cluster Membership/State

NIC

Review the following information on cluster membership and cluster

communication:

■ Cluster membership

At a high level, all nodes configured by the installer can operate as a cluster;

these nodes form a cluster membership. In SF Oracle RAC, a cluster membership

specifically refers to all systems configured with the same cluster ID

communicating by way of a redundant cluster interconnect.

All nodes in a distributed system, such as SF Oracle RAC, must remain

constantly alert to the nodes currently participating in the cluster. Nodes can

leave or join the cluster at any time because of shutting down, starting up,

rebooting, powering off, or faulting processes. SF Oracle RAC uses its cluster

membership capability to dynamically track the overall cluster topology.

SF Oracle RAC uses LLT heartbeats to determine cluster membership:

■ When systems no longer receive heartbeat messages from a peer for a

predetermined interval, a protocol excludes the peer from the current

membership.

■ GAB informs processes on the remaining nodes that the cluster membership

has changed; this action initiates recovery actions specific to each module.

Overview of Veritas Storage Foundation for Oracle RAC

Component products and processes of SF Oracle RAC