17.05 - File System: BLC Columns - Teradata Database

Teradata Vantage™ - Resource Usage Macros and Tables

prodname
Advanced SQL Engine
Teradata Database
vrm_release
17.00
17.05
created_date
June 2020
category
Administration
User Guide
featnum
B035-1099-170K

These columns collect various BLC statistics for use in performance analysis and debugging.

BLC enables data compression at the data block (DB) level of the Teradata Database file system. Compression reduces the amount of storage required for a given amount of data. The BlockLevelCompression field of DBS Control enables and disables BLC.

For more information on BLC and compression-related DBS Control settings, see Teradata Vantage™ - Database Utilities , B035-1102 .

You must enable BLC to collect statistics from the columns below or zero will be returned for each column.
Column Name Mode Description Data Type
FileCompDBs count Total number of data blocks compressed. FLOAT
FileCompDBs_HW count Total number of data blocks compressed by the hardware compression card. This amount is included in the FileCompDBs column. FLOAT
FileCompCPU count Total compression time, including any overhead. The column measures, in microseconds, the time it takes from the beginning of the compression operation to the end. FLOAT
FilePostCompMB count Total number of MBs of compressed data that result from uncompressed blocks being compressed.

This column is used together with the FilePreCompMB column to calculate the compression ratio.

FLOAT
FilePreCompMB count Total number of MBs for the data block that will be compressed before any compression starts.

This column is used together with the FilePostCompMB column to calculate the compression ratio.

FLOAT
FileCompCylMigrs count Number of cylinder migrates done as part of a Ferret COMPRESS command or by the AutoTempComp background task.

The AutoTempComp background task is responsible for finding the cylinders that should be compressed or decompressed based on their temperature. For more information on this background task, see Teradata Vantage™ - Database Design, B035-1094.

For more information on the Ferret utility, COMPRESS command, see Teradata Vantage™ - Database Utilities , B035-1102 .

FLOAT
FileCompFerretDBs count Number of blocks compressed as a result of the compression operation called from the Ferret utility (see Teradata Vantage™ - Database Utilities , B035-1102 ). FLOAT
FileCompTempDBs count Number of data blocks compressed by the AutoTempComp background task because they were colder than the DBS Control TempBLCThresh field setting. See Teradata Vantage™ - Database Design, B035-1094 for more information on the DBS Control TempBLCThresh field and AutoTempComp background task.
You must enable the temperature-based block-level compression (TBBLC) feature when using this column or it will return a zero. To determine if TBBLC is enabled, see EnableTempBLC in Teradata Vantage™ - Database Utilities , B035-1102 .
FLOAT
FilePreUncompMB count Total number of MBs for the compressed data block that will be uncompressed before uncompression starts.

This column is used together with the FilePostUncompMB column to calculate the uncompression ratio.

FLOAT
FilePostUncompMB count Total number of MBs of uncompressed data that result from compressed blocks being uncompressed.

This column is used together with the FilePreUncompMB column to calculate the uncompression ratio.

FLOAT
FileTempCPU count CPU time, in microseconds, spent by the AutoTempComp background task either compressing or uncompressing data, including any overhead.

For more information on the AutoTempComp background task, see Teradata Vantage™ - Database Utilities , B035-1102 .

You must enable the temperature-based block-level compression (TBBLC) feature when using this column or it will return zero. To determine if TBBLC is enabled, see EnableTempBLC in Teradata Vantage™ - Database Utilities , B035-1102 .

Also, any time counted against this column is not counted in either the FileCompCPU or FileUnCompCPU column.

FLOAT
FileUnCompCPU count Total uncompression time, including any overhead. The column measures, in microseconds, the time it takes from the beginning of the uncompression operation to the end. FLOAT
FileUnCompCylMigrs count Number of cylinder migrates done as part of a Ferret UNCOMPRESS command or by the AutoTempComp background task.

For more information on the Ferret utility, UNCOMPRESS command, or AutoTempComp background task, see Teradata Vantage™ - Database Utilities , B035-1102 .

FLOAT
FileUnCompDBs count Total number of data blocks uncompressed. FLOAT
FileUnCompDBs_HW count Total number of data blocks uncompressed by the hardware compression card. This amount is included in the FileUnCompDBs column. FLOAT
FileUnCompFerretDBs count Number of blocks uncompressed as a result of the uncompression operation called from the Ferret utility (see Teradata Vantage™ - Database Utilities , B035-1102 ). FLOAT
FileUnCompTempDBs count Number of data blocks uncompressed by the AutoTempComp background task because they were warmer than the DBS Control TempBLCThresh field setting. See Teradata Vantage™ - Database Design, B035-1094 for more information on the DBS Control TempBLCThresh field and AutoTempComp background task.
You must enable the TBBLC feature when using this column or it will return zero. To determine if TBBLC is enabled, see EnableTempBLC in Teradata Vantage™ - Database Utilities , B035-1102 .
FLOAT