The tdheatmap table function provides a report on the temperature (frequency of access) of table data on a per-AMP basis.
Benefits
- tdheatmap is a built-in Teradata Database table function that replaces the older, stand-alone version, td1410_heatmap.
- Adds new Temperature Percentile, Grade, Media Type, and Storage Class fields to report output.
- Allows creation of heatmap views that can be used to create a heatmap history table for a given table that shows trends in table access.
- The DBC.tdheatmap_m macro included with this feature generates a report with the information generated by the tdheatmap function, and adds fields for database and table names (rather than IDs) and date, time, and cylinder ID.
- Because the heat map for any single AMP generally provides a good representation of all AMPs in the system, the tdheatmap table function is executed on a single, user-specified AMP.
Considerations
- To use this function, the Temperature-Based Block-Level Compression feature must be enabled, or you must have licensed the Teradata Virtual Storage feature.
- If you have previously installed the td1410_heatmap function, this older version will be deleted from the system when you upgrade to Teradata Database 16.00. If you have scripts that reference td1410_heatmap, you must rewrite them to use the new function name, tdheatmap.
- The tdheatmap function executes in non-protected mode.
- Because the function must interface with the several Teradata Database subsystems, it can be costly to run. Because data temperatures do not change quickly, tdheatmap does not need to be run frequently (hourly or daily) unless needed to investigate potential problems.
- Data temperature is a relative concept, so the specific temperature values that determine HOT, WARM, and COLD temperatures may differ between AMPs. This is a consideration when comparing heat map data from different AMPs and from different systems.
Additional Information
For more information on the tdheatmap table function, see Teradata Vantage™ SQL Operators and User-Defined Functions, B035-1210 and Teradata Vantage™ - Database Design, B035-1094.