InterviewSolution
Saved Bookmarks
InterviewSolution
| 1. |
What is Skewness in Teradata? |
|
Answer» As a statistical CONCEPT, "skewness" refers to the row distribution on AMPs (ACCESS Module PROCESSORS). In data distribution, the Skew Factor refers to the distribution of table data among AMPs. Skewed factor of 0 INDICATE that the data is evenly distributed among the AMP's. In the case of highly skewed data, it means that some AMPs have more rows and some have very few, i.e., the distribution is not even. The Skew Factor is high in this case (unequal distribution of data), affecting performance and Teradata's parallelism. Choosing the right index can control the skewness of the data distribution. Ideally, you should choose a Primary Index that contains as many unique values as possible so as to AVOID skewness. |
|