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VCS directs SF Oracle RAC operations by controlling the startup and shutdown of component layers and providing monitoring and notification of failure.
In a typical SF Oracle RAC configuration, the RAC service groups for VCS run as "parallel" service groups rather than "failover" service groups; in the event of a failure, VCS does not attempt to migrate a failed service group. Instead, the software enables you to configure the group to restart on failure.
The High Availability Daemon (had) is the main VCS daemon running on each node. had tracks changes in the cluster configuration and monitors resource status by communicating with GAB and LLT. had manages all application services using agents, which are installed programs to manage resources (specific hardware or software entities).
The VCS architecture is modular for extensibility and efficiency. had does not need to know how to start up Oracle or any other application under VCS control. Instead, you can add agents to manage different resources with no effect on the engine (had). Agents only communicate with had on the local node, and had communicates status with had processes on other nodes. Because agents do not need to communicate across systems, VCS is able to minimize traffic on the cluster interconnect.
SF Oracle RAC provides specific agents for VCS to manage CVM, CFS, and Oracle agents.
SF Oracle RAC uses port h for had communication. Agents communicate with had on the local node about resources, and had distributes its view of resources on that node to other nodes through port h. had also receives information from other cluster members to update its own view of the cluster.
VCS uses two configuration files in a default configuration:
main.cf file defines the entire cluster, including the cluster name, systems in the cluster, and definitions of service groups and resources, in addition to service group and resource dependencies.
types.cf file defines the resource types.
Additional files similar to types.cf may be present if you add agents. For example, SF Oracle RAC includes additional resource types files, such as OracleTypes.cf and PrivNIC.cf.