The following recommendations refer to monitoring and management facilities other than Database Query Logging or Teradata Viewpoint that might be active in a Teradata data warehouse. These recommendations are made with tactical query applications in mind; however, their value should be understood in light of the entire Teradata Database environment.
- Avoid using the account string expansion &T variable for tactical queries, because it is likely to write one row in AmpUsage for every request issued. This extra processing overhead can impact response time and reduces the throughput of single- or few-AMP tactical queries. See Database Administration for more information about account string expansion variables.
- Stop using Access Logging to log queries. Database Query Logging provides most of the same functionality and offers much more. DBQL also has considerably less impact on the performance of tactical query applications. See Database Administration and SQL Data Definition Language for more information about Access Logging and Query Logging.
- Taking frequent snapshots using Priority Scheduler monitor (every 5 or 10 seconds) incurs no meaningful overhead and does not affect tactical query performance. Information from this monitor output can be useful in understanding how priorities are functioning and which groups are using what extent of CPU activity.
- A ten-minute collection interval for ResUsage has proven sufficient in many diverse environments, and minimizes any impact on tactical queries. ResUsage data is critical to tracking overall system-level health and usage patterns, and for capacity planning. See Resource Usage Macros and Tables for more information about ResUsage.