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

traffic is redirected to the remaining links. A maximum of eight network links
are supported.
■ Heartbeat
LLT is responsible for sending and receiving heartbeat traffic over each
configured network link. The heartbeat traffic is point to point unicast. LLT
uses ethernet broadcast to learn the address of the nodes in the cluster. All
other cluster communications, including all status and configuration traffic
is point to point unicast. The heartbeat is used by the Group Membership
Services to determine cluster membership.
The heartbeat signal is defined as follows:
■ LLT on each system in the cluster sends heartbeat packets out on all configured
LLT interfaces every half second.
■ LLT on each system tracks the heartbeat status from each peer on each
configured LLT interface.
■ LLT on each system forwards the heartbeat status of each system in the cluster
to the local Group Membership Services function of GAB.
■ GAB receives the status of heartbeat from all cluster systems from LLT and
makes membership determination based on this information.
Figure 1-5 shows heartbeat in the cluster.
Figure 1-5
Heartbeat in the cluster
HAD
Unicast point to point
heartbeat on every
interface every 0.5
second
Each LLT module tracks heartbeat
status from each peer on each
configured interface
LLT forwards heartbeat
status of each system to
GAB
AGENT
AGENT AGENT AGENT
HAD
GABGAB
LLTLLT
LLT can be configured to designate specific cluster interconnect links as either
high priority or low priority. High priority links are used for cluster
communications to GAB as well as heartbeat signals. Low priority links, during
normal operation, are used for heartbeat and link state maintenance only, and
the frequency of heartbeats is reduced to 50% of normal to reduce network
overhead.
Overview of Veritas Storage Foundation for Oracle RAC
Component products and processes of SF Oracle RAC
26