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

For example, CVM must initiate volume recovery and CFS must perform a
fast parallel file system check.
■ When systems start receiving heartbeats from a peer outside of the current
membership, a protocol enables the peer to join the membership.
■ Cluster communications
GAB provides reliable cluster communication between SF Oracle RAC modules.
GAB provides guaranteed delivery of point-to-point messages and broadcast
messages to all nodes. Point-to-point messaging involves sending and
acknowledging the message. Atomic-broadcast messaging ensures all systems
within the cluster receive all messages. If a failure occurs while transmitting
a broadcast message, GAB ensures all systems have the same information after
recovery.
Low-level communication: port relationship between GAB and
processes
All components in SF Oracle RAC use GAB for communication. Each process
wanting to communicate with a peer process on other nodes registers with GAB
on a specific port. This registration enables communication and notification of
membership changes. For example, the VCS engine (HAD) registers on port h.
HAD receives messages from peer had processes on port h. HAD also receives
notification when a node fails or when a peer process on port h unregisters.
Some modules use multiple ports for specific communications requirements. For
example, CVM uses multiple ports to allow communications by kernel and
user-level functions in CVM independently.
Figure 1-7
Low-level communication
vxconfigd
LLT
GAB
GAB Membership
HAD
VXFEN
kmsg
GLM
GMS
CVM CFS
ODM Oracle
CM API
skgxn
VCSMM
IPC API
skgxp
LMX
a h b v
u, w
f d o
29Overview of Veritas Storage Foundation for Oracle RAC
Component products and processes of SF Oracle RAC