Statistics Collection Recommendations – Teradata 14.10, 15.0 and 15.10 - comment by carrie

RESPONSE TO FIRST QUESTION:  
 
Even if you have usecount logging on, the information is not able to be stored in the statistics  histogram, and therefore cannot be used for extrapolation or to properly assess changes over time from the history records, because you are not using Version 6 histograms.   Not being able to properly assess changes over time across the history records could make it less likely that the optimizer will select a downgrade to sampling.  
 
You only will get Verions 6 histograms when you change the NoDot0Backdown flag.   You should get more accurate extrapolations with the V6 histograms.  
 
The only tradeoff in setting that flag to TRUE  is that you will not be able to back down to an earlier release.   So if there is a possibility you may want to back down you should wait until such time as you are confident you want to remain on 14.10.    I don't know of any particular risks at this time in staying on 14.10 and setting the flag to TRUE, but neither have I been tracking this as a possible issue.   If you really are concerned, talk to the GSC and seek their advice.
 
Thanks, -Carrie