15.00 - TVSTemperature Reserved Storage Management Query Bands - Teradata Database

Teradata Database SQL Data Definition Language Detailed Topics

prodname
Teradata Database
vrm_release
15.00
category
Programming Reference
featnum
B035-1184-015K

TVSTemperature Reserved Storage Management Query Bands

Note: As a general rule, customer‑written applications should not use these query band names. They are reserved for use by Teradata‑written applications and applications written by third party Teradata partners.

However, the TVSTemperature query bands are an exception to this rule because they support both Teradata Virtual Storage and temperature‑based block‑level compression.

Use the TVSTemperature query band for tables whose effective BLOCKCOMPRESSION option is AUTOTEMP. For AUTOTEMP to be active, both BLC and TempBLC must be enabled in DBS Control. In that case the TVSTemperature query band specifies the desired temperature for the table cylinders on which the table data is to be stored. This temperature determines the compressed or uncompressed state of blocks in the table. The DBS Control parameter TempBLCThresh determines which temperatures compress data and which decompress data.

The following somewhat loose definitions apply to the commonly described temperature bands for block-level compression.

 

        Temperature

                                                         Definition

COLD

The 20% of data that is least frequently accessed.

WARM

The remaining 60% of data that falls between the COLD and HOT bands.

HOT

The 20% of data that is most frequently accessed.

VERY HOT

Data that you or Teradata Virtual Storage think should be added to the Very Hot cache list and have its temperature set to very hot when it is loaded using the TVSTemperature query band.

The following query band names are used for TVSTemperature.

  • TVSTEMPERATURE_PRIMARY
  • TVSTEMPERATURE_PRIMARYCLOBS
  • TVSTEMPERATURE_FALLBACK
  • TVSTEMPERATURE_FALLBACKCLOBS
  • You can specify either VERY HOT, HOT, WARM, or COLD for each of these query band names.

    These query bands are valid for both sessions and transactions.

    See Teradata Virtual Storage for more information on these query band name.