AMPs use a DBQL cache called DBQL Performance Stats (DPS) cache. This cache holds DBQL request and step data for active requests.
The DPS cache size is controlled by the DBQL_AWTDPS_CacheMaximum field 37 in the DBS Control Performance section. DBQL_AWTDPS_CacheMaximum limits the size to which the per-AMP AMP Worker Tasks (AWT) DPS cache can grow. The default size of the DPS cache is 8192 KB.
The cache size range is 1024 KB - 16384 KB. The cache holds approximately 2,500 entries per 1024 KB. When the cache is full, DBQL AMP data is not captured. Space in the cache is dynamically reused, but the memory for the cache is not released until the database is restarted. The recommended range is 4096 KB - 10240 KB.
Generally you do not have to adjust these values because the default value of 8192 is optimal for DBQL data collection to handle all types of workload.
For more information, see DBQL_AWTDPS_CacheMaximum in Teradata Vantage™ - Database Utilities, B035-1102.
Perform the following steps to change the DPS cache size:
- For example, increase the DPS cache size to 10240 KB. Modify Performance (p) field 37:
dbscontrol m p 37 = 10240
- Write the DBS control record for the change to take effect:
write