Statistics collection recommendations – Teradata 14.0 - comment by carrie

Hi Andrew,
 
Age, or the passage of time, is a less accurate way of determining when statistics need recollecting compared to using the percent of change as a threshold.  Some tables may change a lot in, say, 7 days, while others may change very little, and still others may not change at all.  
 
Maybe one reason you don't hear much discussion around how to set that type of threshold is that it is inherently difficult to come up with a different ageing algorithm for each table's statistics.   And you would tend to consume unnecessary resources recollecting more often than needed if you base your time threshold on a single number of days for all tables. 
 
What I've seen in terms of time as a threshold is pretty generic:   Recollect on all tables that undergo any level of change weekly, and the ones that undergo larger changes or are more critical, recollect daily.   
 
You might want to post this question on Teradata Forum and see what other Teradata DBAs are doing in this regard.  You would probably get more detailed and anecdotal information doing that.  
 
The new 14.10 statistics enhancements do rely primarily on percent of change as a threshold, but introduce more accurate ways of measuring table change.  There is a default setting in 14.10 called SysChangeThresholdOption which will examine each statistic when it is submitted for collection and decide whether or not a reasonable threshold of change has been met.  If it has not, then that statistic will not be recollected at that time. 
 
This default system threshold setting has access to insert, delete and update counts for the table and only looks percent of change, not age.  However, it only does threshold evaluation if the correct (and new) DBQL logging has been turned on, logging that tracks the update counts for the table. 
 
See the orange book Teradata Database 14.10 Statistics Enhancements for more detail on 14.10 statistics features.
 
Thanks, -Carrie