title: What is bad numbers for skew factor in Teradata?
body: <p>I determine skew factor this way:</p>
  
  <pre><code>SELECT 
  TABLENAME,
  SUM(CURRENTPERM) /(1024*1024) AS CURRENTPERM, 
  (100 - (AVG(CURRENTPERM)/MAX(CURRENTPERM)*100)) AS SKEWFACTOR 
  FROM 
  DBC.TABLESIZE 
  WHERE DATABASENAME= &lt;DATABASENAME&gt; 
  AND 
  TABLENAME =&lt;TABLENAME&gt;  
  GROUP BY 1;
  </code></pre>
  
  <p>For some tables with size ~600 Gb the skew factor is 30%. For table with size 10 Gb is pretty high 98%. How really is bad the number above? Is there any official article saying that more than  10% should be redistributed? I need it to substantiate requirements for mart developer. I have found only <a href="http://digitalhalon.com/blog/2012/02/08/teradata-sql-to-estimate-skew-for-a-table-when-considering-different-primary-indexes/" rel="nofollow noreferrer">this</a> </p>