Recommended Dictionary Statistics to Collect in Teradata 14.0 - comment by carrie

Sadeep,
 
It is normal to get this warning if statistics have been skipped and you do not have USECOUNT logging on.  
 
If you look up that message (or google it), here is what it says:
 
9683:   The DBQL ObjectUsage logging is not enabled. The change percentage to skip statistics collection is determined based on dynamic AMP sampling, which can only detect the row count change.
 
Explanation:
The DBQL ObjectUsage logging is not enabled. The change percentage to skip this statistics collection is determined based on the dynamic AMP sampling which can only detect the row count change. Therefore, the system cannot accurately determine the update and the combination of insert and delete counts on the target table.
 
Notes:
This warning is issued when the DBQL ObjectUsage logging is not enabled and statistics collection is skipped.
Remedy:
Turn on ObjectUsage logging for the target database if more accuracy is needed.
 
Skipping is a technique in Teradata Database 14.10 that the optimizer uses when you have asked for stats recollection but the table does not appear to have changed enough since the last collection to warrant that recollection.  Under those conditions the optimizer may skip the re-collection.  You can read more about skipping in the Teradata 14.10 Statistics Enhancement orange book.
 
In this case, the warning is telling you that skipping happened, but that it did not happen with as much accuracy as it could, if USECOUNT logging had been turned on.  Instead of using actual Update, Delete and Insert counts that you would have available with USECOUNT logging, only random AMP sampling was used, and random sampling only detects a table's growth.  If you deleted as many rows as you inserted since the last collection, random AMP sampling would interpret that as no change, while USECOUNT logging would recognize the change.
 
Thanks, -Carrie