17.00 - 17.05 - Alternate Query Investigation Methods - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - Database Administration

Product
Advanced SQL Engine
Teradata Database
Release Number
17.00
17.05
Published
June 2020
Language
English (United States)
Last Update
2021-01-22
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Problem Action
If the system is CPU-bound or disk-bound, or the processing is skewed.
  • Look at physical resource utilization:

    Use Teradata Viewpoint. Monitor physical resources to view CPU/disk usage by node. Monitor virtual resources to view CPU/disk usage by vproc.

    Look at DBC.ResusageSpma to view CPU, disk, and BYNET usage.

  • Look at workload utilization:

    Use DBQL to find the user with the skewed processing.

  • Look at data distribution:

    Use DBC.TableSizeV to identify tables with skewed data distribution.

If the processing is skewed, identify the user.
  • Use Teradata Viewpoint.
  • Check DBC.SessionInfoV or run Query Session to identify the current user.
  • Check DBC.LogOnOffV to view historical users.
  • Check DBC.AMPUsage to identify the heavy resource user.
  • Check DBC.DiskSpaceV to identify large spool user.
If the processing is skewed, get information on the problematic query.
  • To identify the query, ask the user or check query log.
  • Run EXPLAIN on the query to determine if a bad join plan exists. Look for unexpected product joins. Verify that large tables are not joined before small tables. Look for estimates that are too high or too low.