17.00 - 17.05 - Changing DBQL Cache Size - Advanced SQL Engine - Teradata Database

Teradata Vantage™ - Database Administration

Product
Advanced SQL Engine
Teradata Database
Release Number
17.00
17.05
Published
June 2020
Language
English (United States)
Last Update
2021-01-22
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Use the following procedure to change how much data DBQL caches hold before writing to Data Dictionary tables. Cache size also determines whether DBQL uses 64 KB or 1 MB data blocks for disk writes. Increasing the cache size reduces overhead and resource contention and improves performance. Although 2 MB is optimal in most cases, consider increasing the cache size if detailed query logging is enabled and queries experience resource contention.
  1. Flush all DBQL caches so that their contents are not lost during the required system restart:
    FLUSH QUERY LOGGING WITH ALL;
  2. Determine the current value of the DBS Control field DBQLDefCacheSize, which is in the Performance group.
    DISPLAY PERFORMANCE
  3. Change the value of DBQLDefCacheSize:
    MODIFY PERFORMANCE 35 = value
    Valid values are from 0 to 16 MB, where 0 sets the cache size to 64 KB and the data block size to 64 KB. Choose a size larger than 0 to set the data block size to 1 MB and increase the cache size of almost all DBQL tables.

    The DBQLParamTbl cache size is controlled separately by DBS Control field 30, DBQLLOBCacheSize. DBQLParamTbl is populated when you begin query logging with the PARAMINFO option.

  4. Restart.