Internode Communication (INC)

INC provides transactional communication between coordinator and secondary nodes.

INC links exist between the coordinator to the secondary nodes and from secondary nodes to the coordinator, but not between secondary nodes.

Secondary servers communicate with the coordinator via INC for executing DDL and read-write DML statements. The coordinator communicates with the secondary servers via internode communication when certain stored procedures are executed on the coordinator. Secondary servers never communicate with each other using INC.

The INC link consists of heartbeat and pooled connections.

• Heartbeat Connections
  Every secondary node has a heartbeat connection, a dedicated connection to the coordinator node. This connection is established at the time of secondary node startup and remains active as long as the secondary node is active.
• Pooled Connections
  Each secondary node maintains an INC connection pool. The connection pool manages connections from the secondary node to the coordinator node used by INC for transactional communication.