Webinar: Histograms: Pre-12c and Now

To improve optimizer estimates in case of skewed data distribution , histograms can be created. Prior to 12c, based on No. of distinct values (NDV) in a column two types of histograms could be created :

if no. of buckets >= NDV, frequency histogram is created and the optimizer makes accurate estimates.

If no. of buckets < NDV, height balanced histogram is created and accuracy of optimizer estimates depends on whether a key value is an endpoint or not.

The problem of optimizer mis-estimates in case of height balanced histograms is resolved to a large extent in Oracle Database 12c by introducing top-frequency and hybrid histograms which are created if no. of buckets < NDV.

I will present a webinar on “Histograms: Pre-12c and now” on Saturday, November 7th  at 10:00 AM – 11:00 AM (IST) organized by All India Oracle User Group – North India Chapter.

This webinar explores Pre as well post-12c histograms while highlighting the top-frequency and hybrid histograms introduced in Oracle Database 12c.

Everyone can join this Live Webinar @


Hope to meet you at the webinar!!!

3 thoughts on “Webinar: Histograms: Pre-12c and Now

  1. I wished to participate but unfortunately I found that 10 AM IST is equivalent to 4 AM in Czech Republic where I live. It would be nice to record the event and share the recording afterwards :)
    Thanks ,

Your comments and suggestions are welcome!