Oracle Interconnect RAC

Cluster Private Interconnect

The cluster interconnect is a high bandwidth, low latency communication facility that connects each node to other nodes in the cluster and routes messages among the nodes. It is a key component in building the RAC system.

In case of RAC database, the cluster interconnect is used for the following high-level functions:

Monitoring Health, Status, and Synchronize messages
Transporting lock management or resource coordination messages
Moving the Cache Buffers (data blocks) from node to node.

High performance database computing involves distributing the processing across an array of cluster nodes. It requires that the cluster interconnect provide high-data rates and low-latency communication between node processes.

Here's a few ways to find information about interconnect and troubleshoot any issues...

1. select * from gv$cluster_interconnects ;

2. Using the clusterware command oifcfg:
$ oifcfg getif
eth2 100.100.90.0 global public
eth0 192.168.10.0 global cluster_interconnect
eth1 192.168.11.0 global cluster_interconnect

3. Using oradebug ipc:
sqlplus “/ as sysdba”
SQL> oradebug setmypid
SQL> oradebug ipc Information written to trace file.

The above command would dump a trace to user_dump_dest. The last few lines of the trace would indicate the IP of the cluster interconnect. Below is a sample output.
From the trace file on node1:

SSKGXPT 0×5edf558 flags SSKGXPT_READPENDING socket no 9 IP 192.168.11.1 UDP 18852
From the trace file on node2:

SSKGXPT 0×5edf558 flags SSKGXPT_READPENDING socket no 9 IP 192.168.10.2 UDP 38967