Skew Exception Criteria | Teradata Vantage - 17.10 - Skew Exception Criteria - Advanced SQL Engine - Teradata Workload Management

Teradata Vantageā„¢ - Workload Management User Guide

Product
Advanced SQL Engine
Teradata Workload Management
Release Number
17.10
Release Date
July 2021
Content Type
Administration
User Guide
Publication ID
B035-1197-171K
Language
English (United States)

A skewed request can severely impact the parallel efficiency of the system, eliminating the benefit of multiple AMPs. If the system is processing one skewed request step, all the AMPs with less processing to do must wait until the single skewed AMP with more processing to do completes. Only the skewed AMP runs at capacity while the other AMPs sit idle. In a mixed workload, the skewed AMP cannot respond as quickly as the other AMPs because it is clogged with skewed processing. All requests in the system can slow down when there is a skew.