Re: Way to determine UPDATE STATISTICS

Jung-Hui The informix recommended rule for UPDATE STATISTICS is as follows: 1) MEDIUM WITH DISTRIBUTIONS for all columns that are not part of an index. 2) HIGH for all columns which head an index. 3) LOW for all index columns that do not head an index. I had heard that it has changed in recent versions, but this seems to work on my setup (IDS 7.24 / HP-UX 10.20). The RESOLUTION is the number of bins in the index. A bin is a container thingy that holds a set of key values. The resolution is expressed as a percentage so specifying a resolution of 2.5 will cause 40 bins to be created (ie 2.5% of the data is contained in a single bin therefore number of bins = 100/2.5). Decreasing the RESOLUTION will lead to the creation of more bins, which means that the query optimizer will be able to determine with greater accuracy the path to be followed when key values in the table(s) are not uniformly distributed. For more information, RTFM Guide to SQL - Syntax or Liz Suto's book on Peformance Tuning. HTH Sujit ______________________________ Reply Separator _________________________________ Subject: Way to determine UPDATE STATISTICS Author: cheng@dbtel.com.tw (Jung-Hui Cheng) at internet Date: 12/16/1998 5:18 AM Hi All; Is there a method to determine the rule about update statistics ? For example, what kind of tables should be run "UPDATE STATISTICS HIGH" and others use "LOW". By the way, what is the "RESOLUTION" ? How it work ? Thanks Jung-Hui Cheng cheng@dbtel.com.tw