DBQL Metrics - response (1) by dnoeth

Total = sum of all AMPs CPU/IO usage
Max = maximum CPU/IO usage across all indicidual AMPs
Skew = Comparing Max with Avg usage. On a parallel system the slowest AMP determines the speed, when the work is not evenly spread across AMPs it's slowing down the elapsed time and might withhold resources for other queries
 

CASE
   WHEN (AMPCPUTime / (HASHAMP()+1) ) =0 OR NumOfActiveAMPs = 1 THEN 0 
   ELSE MaxAmpCPUTimeNorm/(AMPCPUTimeNorm / (HASHAMP()+1) ) 
END

 
Impact = Max * number of AMPs in system, i.e. resource usage based on Skew
CASE WHEN NumOfActiveAMPs = 1 THEN MaxAmpCPUTime * (HASHAMP()+1) 
 
Wastage = don't know probably Impact - Total

Have a look at the definition to see the exact calculation used at your site.

Dieter