ResUsage and Disk Utilization
The ResNode macro reports disk utilization averages by second.
Parallel Disk Efficiency
Parallel AMP efficiency does not necessarily match parallel disk efficiency. Monitor parallel disk efficiency using ResUsageSvdsk and ResUsageSpdsk tables.
The following table lists common mistakes that can cause skewing and poor parallel efficiency and suggests solutions.
|A user did not define a PI. The system uses the first column of the table as the default P1.||Define a PI with good data distribution.|
|A user used a null as PI for the target table in a left outer join.||Perform any of the following:
|A user performed a join on column with poor data distribution. For example, the user entered:
SELECT A.colname, B.x, B.y FROM A, B WHERE A.colname = B.colname;