Tactical Workload Exceptions | Teradata Vantage - 17.00 - Tactical Workload Exceptions - Teradata Workload Management

Teradata Vantageā„¢ - Workload Management User Guide

prodname
Advanced SQL Engine
Teradata Workload Management
vrm_release
17.00
created_date
June 2020
category
Administration
User Guide
featnum
B035-1197-170K

All Tactical workloads have an associated Tactical Exception that identifies and acts on requests that have non-Tactical characteristics. If a resource-intensive request starts to run in a Tactical workload, TASM demotes that request to another workload.

TASM monitors the following criteria, either of which can trigger a tactical exception:
  • Tactical CPU Time
  • Tactical I/O Physical Byte
TASM changes the workload of a request if the request exceeds either of the following Tactical CPU Time thresholds:
  • CPU (sum over all nodes) in CPU seconds
  • CPU per Node in CPU seconds
TASM changes the workload of a request if the request exceeds either of the following Tactical I/O Physical Byte thresholds:
  • I/O (sum over all nodes) in KB, MB, or GB
  • I/O per Node in KB, MB, or GB

When a request exceeds a per node limit, the request is demoted on that one node only. When a request exceeds a sum over all nodes limit, the request is demoted across all nodes. It is possible that a request can exceed a per node limit on one or more AMPs but not exceed the sum over all nodes limit. In that case, the request could run in different workloads on different nodes. One way to keep requests running in the same workload on all nodes is to set the per node and sum across all nodes thresholds to the same value.

If DBQLogTbl logging is enabled, the number of nodes that reach the per node threshold is logged in the following fields:
  • CPU: TacticalCPUException
  • I/O: TacticalIOException

By default, the sum over all nodes CPU and I/O thresholds are automatically set at the per node setting multiplied by the number of nodes in the system. To change this default, use the Tactical Exception tab on the Workloads view.

Tip: If you add or replace hardware, TASM does not automatically adjust the CPU and I/O sum over all nodes settings. Always recheck these values after a reconfiguration to make sure they fit the new platform.
Tip: Teradata recommends that the Tactical CPU Time thresholds CPU (sum over all nodes) and CPU per Node be set above 1 second. Checking more often than every 1 second can add considerable overhead and impact active work.