15.00 - Cases Where Negative Performance Effects Are Most Likely To Occur - Teradata Database

Teradata Database Design

prodname
Teradata Database
vrm_release
15.00
category
User Guide
featnum
B035-1094-015K

Cases Where Negative Performance Effects Are Most Likely To Occur

The greatest decrement in the performance of querying column‑partitioned tables occurs when the following conditions take place.

  • Most or all of the columns in a column‑partitioned table are projected by a request.
  • The request is not selective.
  • The table being queried has thousands of column partitions.
  • The retrieval performance for a column‑partitioned table or join index is not good when the number of column partition contexts that are available is significantly fewer than the number of column partitions that must be accessed to respond to the query. Note that there are at least eight available column partitions contexts. Depending on your memory configuration, there may be more available contexts.
  • When this happens, consider the following remedies.

  • Reconfigure the table or join index to decrease the number of column partitions that need to be accessed by combining column partitions so there are fewer of them.
  • If there is enough memory available, increase the setting for the DBS Control parameter PPICacheThrP.
  • The table being queried has enough row‑partitioned levels that there are very few physical rows in populated combined partitions, and the physical rows contain only one or a few column partition values.