Unexpected Teradata System Failure | Teradata Unity - 17.00 - Unexpected Teradata System Failure - Continuous Availability - Teradata Unity

Teradata® Unity™ User Guide

Product
Continuous Availability
Teradata Unity
Release Number
17.00
Published
September 2020
Language
English (United States)
Last Update
2020-09-15
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If a Teradata system fails unexpectedly, Unity automatically re-routes client applications using passive or managed routing if the routing rules allow the applications to run on another system.

When a system fails unexpectedly, managed sessions continue without noticeable interruption because the managed sessions are already connected to multiple systems in parallel. If a managed session is reading a large multi-packet response from the failing system, the current request fails, with a limited impact.

Passive sessions automatically reconnect to the other Unity system. In such cases, passive sessions lose inflight volatile data but are able to continue processing.

The failed Teradata system is marked Interrupted and new connections are automatically diverted from connecting to it until it reconnects to the Teradata system using the unitymgmt user. Unity automatically re-processes requests that the failed Teradata system missed while it was down. When the system is restored, Unity returns it to the Active state and resumes online work on the system.