Examine Logged Data | Teradata Vantage - 17.00 - 17.05 - Examining the Logged Data - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - Database Administration

Advanced SQL Engine
Teradata Database
Release Number
June 2020
English (United States)
Last Update

First-level information is captured in DBQLogTbl and DBQLSummaryTbl. For short-running, high-volume queries, you can request the THRESHOLD option in combination with the SQL, STEPINFO, or OBJECTS logging option to reduce collection overhead. You can further specify the units of elapsed time, CPU usage, or number of I/Os.

Use the data from DBQLogTbl and DBQLSummaryTbl to identify issues such as workloads that do not meet response time service-level agreements. If space is a major concern, you can use threshold logging, but having the detail can provide much more insight.

Best practices for DBQL logging dictate that you log at the system level with the SQL and OBJECTS logging options. If there are specific account strings, or user IDs that only do millions of tactical, subsecond requests, Teradata recommends that you use the THRESHOLD logging option with the STEPINFO logging option to log CPU usage.

When used selectively, detailed data can be invaluable. Analyze it to:
  • Optimize queries or your query management or priority strategy; for example, compare:
    • Results of different queries that target the same join index
    • Elapsed times of the same query run on different days or hours
  • Determine reasons for high consumption or poor performance by correlating DBQL data to other data collections with query characterization, including QCF, ResUsage, and DBC.AMPUsage
  • Make efficient use of existing capacity and plan for future expansion by factoring in exponential growth of query demand