Error Handling for Writes for Managed Sessions | Teradata Unity - 17.00 - Error Handling for Writes for Managed Sessions - 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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For Write operations, Unity does not wait for all responses from each Teradata Database system. Unity checks the first response for successful operation or error code. Errors include communication failures, memory errors, disk space, and database errors.

System Response Type Description
First Response Successful operation Unity notifies the client application.
Error code All Active Teradata Database systems must return a response before the client application receives one. The Active Sequencer uses a voting mechanism to determine which response is the most common successful response, and sends that response back to the client application. If no successful response is available, the most common error response returns to Unity. If a responses are tied, the first response that Unity receives returns to the client application.
Return to Client Error code listed in the Error Profile for exit Unity returns the error and exits the session on all Teradata Database systems.
Successful operation Unity compares results of the remaining Teradata Database systems to determine consistency of data across Teradata Database systems. The response sent back to the client is final, so all responses from the remaining Teradata Database systems must match.

Unity uses the activity count (number of rows) to indicate data consistency for all INSERT, DELETE, UPDATE, and MERGE statements. The activity count from all Teradata Database systems must match with the activity count of the response sent back to the client. The activity count is not checked for any other types of Write operations. For these type of statements, Unity only checks for statement success or failure. If the activity count or success/failure status of the Write operation does not match, Unity automatically changes the table state to Interrupted or Unrecoverable depending on the type of statement.