Specifies the maximum threshold number of outstanding I/O operations that can exist on a node above which the background temperature-based block-level compression (TBBLC) task pauses for a short period before running again. If the system remains busy, the process waits according to the interval defined by TempBLCInterval.
This field is effective only when TBBLC is enabled.
1 through 1,000
Changes Take Effect
After the DBS Control Record has been written.
This field limits the impact of TBBLC on foreground workloads.
Data temperatures refers to frequency of access:
- Hot data is frequently accessed.
- Cold data is infrequently accessed.
- Warm data is accessed moderately frequently.
Data temperature is measured separately for each AMP at a cylinder level and is a relative measure because the temperature of cylinders can change even if the data it is not directly accessed. This is because it depends on how often other cylinders are accessed in comparison. TBBLC automatically compresses cold data to save storage space and decompresses Warm or Hot data if it was previously Cold (and thus compressed). At any time, different portions of a table, which are spread among many cylinders, may exist in different states of compression depending on their temperatures.
BLC enables data compression at the data block (DB) level of the 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…||See…|
|Block-Level Compression||Teradata Vantage™ - Database Design, B035-1094.|
|BLOCKCOMPRESSION table attribute||Teradata Vantage™ - SQL Data Definition Language Syntax and Examples, B035-1144.|
|Ferret COMPRESS, UNCOMPRESS, and FORCE commands||Ferret Utility (ferret).|
|Query bands for compression||Teradata Vantage™ - SQL Data Definition Language Syntax and Examples, B035-1144.|
|Storage group of DBS Control fields||Storage Group.|