16.10 - Logging Overhead - Teradata Database

Teradata Database Administration

Teradata Database
Release Number
April 2018
English (United States)
Last Update

Before you enable logging, first consider how much and what sort of data you need for adequate analysis. The more information you ask for and the more users you track, the higher the cost to performance and the faster the logs will grow. However, you can specify summary and threshold limits to obtain meaningful data with minimal cost.

The following table lists examples that describe the overhead incurred per user and account.

IF the collection type is … THEN logging is per … AND overhead entails … IN the following log(s) …
default (no options specified) query one default row per query DBQLogTbl
individual, because the query ran longer than THRESHOLD seconds query that runs in more time, or used more CPU or I/O limits one default row per long-running query DBQLSqlTbl, DBQLStepTbl, DBQLObjTbl, and DBQLogTbl
counts of queries that complete within SUMMARY intervals query that runs in less time, or used less CPU or I/O limits when the query count is >0, one row per logging interval (every 10 minutes).

Possible maximum is four rows every 10 minutes for the duration of the session

steps process detail query one row for each step generated DBQLStepTbl
object detail query one row for each object used to resolve the query DBQLObjTbl
explain detail query as many rows as it takes to capture the complete explain text.

The explain text is not formatted. Collecting explain detail has some performance impact.

SQL text detail query as many rows as it takes to capture the complete text of the SQL request DBQLSQLTbl
XML query plan detail query as many rows as it takes to capture the complete XML plan. The XML plan includes the SQL request and other things such as the EXPLAIN text
For more information, see SQL Request and Transaction Processing.
XML lock logging lock of qualifying duration as many rows as it takes to capture the XML lock plan DBQLXMLLOCKTbl