16.10 - Automatic Failover - Teradata Unity

Teradata Unity User Guide

Product
Teradata Unity
Release Number
16.10
Published
January 2018
Language
English (United States)
Last Update
2018-03-29
dita:mapPath
anz1496162519675.ditamap
dita:ditavalPath
ft:empty

In automatic failover mode, the Watchdog process initiates a failover process if all of the following conditions are met:

  • The secondary Sequencer connects to all systems in the Unity cluster before losing the primary Sequencer. This condition verifies that basic network connectivity is valid.
  • The Watchdog confirms that the other Sequencer has not communicated with any of the systems in the Unity cluster.
  • The Watchdog communicates with all managed Teradata systems and verifies the Dispatcher on the other Unity server has not sent updates.
  • All these conditions must be true for the entire wait period defined in the HAAutoFailoverWait configuration value.

During an automatic failover, the Watchdog process waits before initiating a Sequencer failover. The Watchdog confirms the active Sequencer is not running.

The Sequencer process emits a heartbeat every five seconds (default). The heartbeat frequency is defined in the ProcessPingInterval configuration parameter. The ProcessTimeout configuration parameter defines how long the Watchdog process waits for a heartbeat before it allows automatic failover to the Standby Sequencer process.

The Watchdog process might not receive heartbeats if either of the following occur:
  • The Sequencer, network, or server fails
  • The Sequencer process is unresponsive