Storage Foundation for Oracle® RAC 7.4.1 Administrator's Guide - Linux
- Section I. SF Oracle RAC concepts and administration
- Overview of Storage Foundation for Oracle RAC
- About Storage Foundation for Oracle RAC
- Component products and processes of SF Oracle RAC
- About Virtual Business Services
- Administering SF Oracle RAC and its components
- Administering SF Oracle RAC
- Starting or stopping SF Oracle RAC on each node
- Administering VCS
- Administering I/O fencing
- About the vxfentsthdw utility
- Testing the coordinator disk group using the -c option of vxfentsthdw
- About the vxfenadm utility
- About the vxfenclearpre utility
- About the vxfenswap utility
- Administering the CP server
- Administering CFS
- Administering CVM
- Changing the CVM master manually
- Administering Flexible Storage Sharing
- Backing up and restoring disk group configuration data
- Administering SF Oracle RAC global clusters
- Administering SF Oracle RAC
- Overview of Storage Foundation for Oracle RAC
- Section II. Performance and troubleshooting
- Troubleshooting SF Oracle RAC
- About troubleshooting SF Oracle RAC
- Troubleshooting I/O fencing
- Fencing startup reports preexisting split-brain
- Troubleshooting CP server
- Troubleshooting server-based fencing on the SF Oracle RAC cluster nodes
- Issues during online migration of coordination points
- Troubleshooting Cluster Volume Manager in SF Oracle RAC clusters
- Troubleshooting CFS
- Troubleshooting interconnects
- Troubleshooting Oracle
- Troubleshooting ODM in SF Oracle RAC clusters
- Prevention and recovery strategies
- Tunable parameters
- Troubleshooting SF Oracle RAC
- Section III. Reference
Group Membership Services/Atomic Broadcast
The GAB protocol is responsible for cluster membership and cluster communications.
Figure: Cluster communication shows the cluster communication using GAB messaging.
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. 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.